Some of the best teachers I've met came through the Teach for America pipeline. Young, zealous, and super-smart. Very decent folks.
So why the provocative title to this post?
Perhaps I should have said, "How TFA might gut public education." That may be more accurate. Karl Marx was famous for running all problems through an economic filter, and there may be something worthwhile in asking, "What's the cost/benefit of a TFA teacher versus other teachers?"
This might be too vague. Let's take it from another angle: in this time of scarcer resources, are administrators "better off" hiring inexperienced but enthusiastic teachers or "seasoned" (i.e., old) teachers with years of experience and advanced degrees?
In the current education climate, "better off" is often defined as appearing to always do more with less; maximizing resources, in other words. Since public education tends to mimic corporate structures, the goal is to have interchangeable teachers who can do whatever needs to be done. Since individuality is really a matter of indifference, then Cheapest is Best.
So, yes, administrative careerists will naturally use "raw material" that is cheap in order to keep within budget. That's to be expected.
Teach for America is having some unintended consequences. Ultimately bringing down wages and exchanging experience and competence for enthusiasm may be just two.