I'm pretty much convinced of this as well - many of the "converted" never actually seem to have much of a clue about TOE. Moreover, I suspect a lot of them become creationists and think "well I guess that means I must have been an evolutionist before" without really having considering their position in any detail previously.
The sad fact is that people in general have little to no knowledge of evolution in the first place, so "conversion" to creationism is no big deal. Science is not a strong point for Western Civilisation (or at least the English speaking sector).
I'm reaching now - the most "convinced" are those who convert due to some traumatic experience - the youth earth stuff then becomes tied-up to the "solving" of that experience via conversation. Because if it's not all true, then maybe none of it's true and those "bad things" were real, could happen again etc etc.
I don't think so... many Christians are raised in Christian families, and evolution is debunked from an early age. But I agree that YE is often inextricably (but erronously IMO) tied to that person's Christian faith.
Or were you refering only to Christians who had once been "believing evolutionists"?