So, maybe you read in the New York Times that Teach for America alumni are a bunch of burned out deadbeats who have dropped out of civil society in favor of whatever it is that burned out deadbeats do when they stop teaching. I mean, the Times didn't use those exact words, per se, but the attitude was there and that was kind of the slant of the article.
The actual gist was essentially that TFA alumni (those who complete their two year commitments) have lower rates of civic engagement - as measured by voting, charitable giving, etc - than those who leave the program early or are accepted to the program but opt not to join, according to a study out of Stanford. Eduwonk has a pretty good take on the study here that shows the picture may not be quite as bleak as the Times makes it out to be.
What it boils down to really is that TFA does an excellent job identifying and recruiting people who are and are going to be engaged in their communities - voting rates even among the deadbeat crowd are nearly double the national average - but that the TFA experience itself doesn't help get people more involved in a broadly defined way.
I don't want to be an apologist, but I don't see that as a very big deal. The alumni are still more likely to be involved than the average person and they're also much more likely to be involved in educational issues. Given the goal of the organization (to transform and improve education from both within and outside the classroom), the dip in charitable giving is something that I can deal with.