There are an estimated 5 to 6 million Americans living outside the US. The IRS only takes statistics every 5 years on Forms 2555 (FEIE) and Form 1116 (FTC), and the latest is for 2006.
Form 2555 - 334,851 filed (worldwide)
Form 1116 - 2,941,952 filed (total). But only 968,652 were in the general limitation income category. Only 317,831 listed a foreign country.
Of course, there must be many who fall below their respective filing threshold, or have no need to file the above forms.
I would guess there are 1 or 2 people who may be saying to hell with it. With new legislation these figures may change significantly. And, the requirement to file probably won’t change anytime in the near future. As the IRS now states on all such issues, we chose to live in a foreign country. So, no surprises there. (Better the Devil you know,…..?)
There's a fuzzy statistic that claims 45% of all Americans living in the US pay no tax to the IRS. That probably won't change.
(Yes, I know: boring old git. Talk about useless information.)
http://www.irs.gov/taxstats/indtaxstats/article/0,,id=96621,00.html