But for most Americans, the threat of terrorism seems to have become little more than background noise. Just last week, a major terrorist plot was reportedly foiled in Germany, but the average person in the United States probably didn't even hear about it.
Have we become complacent? Or have we just accepted the possibility of terrorism as a normal fact of life and gone about our business?
Hall County Sheriff Steve Cronic thinks the six-year hiatus without another U.S. attack may have created a false sense of security.
"I worry that as Americans, we seem to have short memories," he said. "To me, (9/11) seems like it was yesterday. On my uniform, I still wear a pin of the Twin Towers. I don't think we can say, 'It was a fluke. It won't happen again.' Being a free society makes us vulnerable."
But there's no question that some parts of the United States are more likely to be hit by terrorists. In mostly rural Northeast Georgia, people may be justified in thinking that they are safer.
"I don't think Georgia has many national targets. If (Osama) bin Laden were to target something in Georgia, he would look irrational to his followers," said Bill Chittick, emeritis professor of international affairs at the University of Georgia.
"Terrorists are not just out to kill people. It's about symbolism. If you bombed a football stadium on game day, it would certainly kill a lot of people. But it would not be meaningful to the terrorists."
Chittick said the Twin Towers and the Pentagon were targeted because they represented two strongholds of America's power: capitalism and the military.
After 9/11, Congress and the Bush administration created the Department of Homeland Security and divvied up billions of dollars in anti-terrorism funding to state and local governments.
Cronic said Hall County has received about $3 million in federal grants, using it to buy equipment for responding to incidents such as bomb threats and hazardous-material spills.
Such equipment was sorely needed by small-town police and fire departments, just for their day-to-day operations. But it will probably never be used for actually fighting terrorism.
This year, Congress revamped the funding formula so that more of the money would go to places that are obvious terrorist targets, such as New York City.
"I don't think that Hall will get any funding this year," said William Wright, the county's emergency management coordinator. "Atlanta's airport is considered a target, but Gainesville's would not be."
U.S. Rep. Nathan Deal, R-Gainesville, said the restructuring made sense, though some members of Congress were disappointed at not being able to bring home more dollars to their constituents.
"At the beginning, everybody wanted to get in on the Christmas tree, and that money tricked down to almost every law-enforcement agency in the country," he said. "But we (in Congress) recognized that some areas are more vulnerable."
Are there terrorists among us?
While Cronic agrees that it's unlikely a terrorist from the Middle East would want to bomb Gainesville, he points out that there are American citizens who also have the potential to cause harm.
"Think about the Oklahoma City and the (Atlanta) Olympic Park bombings," he said. "Not all terrorism is international. It can be homegrown, and can be carried out by anyone who has the knowledge and capability, which is easy to get these days through the Internet."
Cronic adds that it would not be difficult for a terrorist to hide in Gainesville, a town with a large population of illegal immigrants.
"It is possible for terrorist cells to come into the country through Mexico, and that's something we need to be aware of," he said.
The influx of immigrants passing through Gainesville has made Hall County a key conduit for the illegal drug trade, Cronic said, and the same pathway could be used by terrorists.
"They will find the path of least resistance," he said. "I'm really worried about this new federal law that will allow trucks to come into the U.S. from Mexico. What was the government thinking? It would be easy to make a bomb out of a truck full of fertilizer."
Deal said he shares Cronic's concern. "There are known incidences of terror suspects taking Spanish classes so they can get into the United States through Mexico," he said. "Reforming immigration law has to be a main component of homeland security."
Douglas Young, a professor of political science at Gainesville State College, thinks the government's focus on airline security may be forcing terrorists to seek other points of entry.
"We've made it much harder for a terrorist to fly into the country, but we're doing a terrible job of protecting our southern border," he said.
Flying the not-so-friendly skies
Airports are generally the only places most Americans are confronted with the possibility of terrorism. For travelers, federal security rules are at best a nuisance. At worst, they may seem arbitrary and even silly.
For example, because one airline passenger tried to set his shoe on fire, millions of people now have to remove their shoes before they're cleared to board a plane.
And because of a single incident last year in which someone might have carried a small amount of explosives, all liquids were initially banned. Then liquids were allowed again, but only in three-ounce containers carried in a one-quart clear bag.
The rules have triggered much griping, partly because passengers don't understand how these measures protect them from terrorists.
Why, they ask, are liquids considered dangerous one day and OK the next? How does adding one more ounce to a 3-ounce container suddenly make it deadly? Why are nail clippers and cigarette lighters forbidden one day and then allowed the next?
Doug Hanson, a Gainesville resident who travels frequently by air, said it is "a little disconcerting" when the rules change, and it does take extra time to go through security screening.
"But I think it's the best way to make sure everyone on board is safe," he said. "I just try to have a good attitude about it. I'll take my shoes off, let them go through my luggage, whatever they want me to do."
Young thinks passengers just have to accept the rules, because air travel is not going to get any easier.
"Many people are unhappy about the security measures at airports. And it's true that there is some bureaucratic incompetence," he said. "But I think our government has erred on the side of caution. I personally feel safer, and I don't know anybody who doesn't fly, at least domestically, because they're afraid of terrorism."
Do security laws threaten freedoms?
A more worrisome issue for those who pay attention to current affairs is whether the tactics some federal agencies say they need in order to root out terrorists may trample on the civil liberties of law-abiding citizens.
"I don't think we should become an Orwellian state and erode the Bill of Rights in the name of security," said Young. "But it's definitely a balancing act. Some of that intelligence must be working, because I think it's way more than a coincidence that we've gone six years without another Muslim terrorist attack."
Deal said some methods, such as the ability to tap into people's phone conversations, are necessary in order for intelligence agencies to do their jobs. But he is mindful of the effect these laws may have on innocent people.
"There's a trade-off in a free society," he said. "But we have always leaned toward protecting constitutional freedoms."
Chittick thinks the Bush administration has gone too far in exerting its executive powers.
"We've lost the constitutional system of checks and balances within our own government," he said. "We're trying to maintain our values at the same time we're fighting the terrorists, but it's difficult to know where to draw the line. If we do things that violate civil liberties, we risk alienating large segments of our own society."
And alienation itself seems to draw certain people into terrorism. Deal thinks that may be why, in recent years, there have been more terrorist incidents in Western European nations than in the U.S.
"Some other countries may have a greater percentage of their population that is disenchanted with their government than we do," he said.
'Hope for the best, prepare for the worst'
Will terrorism ever be eliminated as a major global threat? Will life ever be "normal" again?
Chittick is not optimistic. "To me, the biggest threat is the hatred and despair toward us from radicals, and I don't think that has diminished," he said.
"Over the long term, we have to deny them a base of support. The initial thinking was that if we took out the leadership, like cutting off the head of a snake, that would take care of everything. But terrorism is no longer centralized, and it's harder to locate smaller cells."
Deal believes it is possible to make the United States more secure.
"I think we are safer now," he said. "The absence of an attack (for six years) indicates that we have made great strides. And there are many (legislative) things coming along that have not yet been finalized, such as a national ID bill."
Wright believes the most practical approach is to be prepared if an attack does occur.
"We can't prevent a terrorist attack any more than we can prevent a tornado from touching down," he said. "The bad thing about terrorism is that it's hard to identify the enemy, and you don't know what's going to happen until it happens. That's why we take an all-hazards approach, where we can respond quickly to both natural and man-made disasters."
Cronic, whose philosophy is to "hope for the best and prepare for the worst," said the silver lining of the 2001 tragedy was that it brought about reforms in law enforcement.
"What came about as a result of 9/11 was a great deal of interagency cooperation," he said. "Everybody's working from the same playbook, everyone's connected to the National Incident Management System."
Fear of terrorism did create a lot of unnecessary work for law enforcement, especially during the first few months after 9/11. Local agencies responded to hundreds of calls about bomb threats and to reports of "anthrax" that turned out to be flour or talcum powder.
But Cronic said he would never dismiss someone's complaint without checking into the situation. "We can't afford not to take bomb threats seriously," he said.
"We've got to be realistic. There is another attack coming."