malmo, i'm sympathetic to your viewpoint, and i think on an individual level the choice has to depend in part on a realistic sense of your long-term running career.
if you are someone who is unlikely to make more than 2-3 national teams, then i think you'd be a fool to pass up the opportunity to run with a US jersey on.
similarly, if for some reason your training schedule allows for a full peak at this time of year, with a month or so or moderate down time after the race (a fall marathon perhaps?), then i think you go.
but if you're someone who is near the end of your career (think culpepper, meb, goucher, abdi), you've worn the national team uniform multiple times and you are hoping for either a great track season or a big spring marathon, then i completely understand taking the selfish route.
i don't think i'd blame it on terrorism or even the travel time. the risk of the former i think (and fervently hope) is overblown in the U.S. the latter, i think, can be managed - a few days in europe one or both directions.
rather, i'd just take a realistic look at my chances of placing well, compared to my chances at other international competitions. with the weather the way it will be, i understand not wanting to bother going just to run a terrible race. especially considering the perhaps unfortunate fact that under the best of circumstances our guys aren't fighting for the top spots in the race.
lastly, if you are near the end of a distance running career, you have to think about finances. if a major marathon offers you a couple tens of thousands of dollars, you probably need to take that money. running is just not that lucrative and if you've put off other things in your life for 10-12 years, you've earned the right to be selfish.