Actually, the talk.origins newsgroup -- a Usenet discussion forum dedicated to this topic -- maintains a lengthy list of people who have admitted to having switched from being a creationist to an evolutionist as a result of the discussions on that forum, or from other such debates.
Last time I checked, they couldn't find a single person who personally claimed to have been "converted" in the other direction.
Plenty of Freeper creationists have claimed in the past to have been "converted" from evolution to creationism. Funny thing is, to a man, they fail to be able to state the theory of evolution. They all proudly disavow cartoon versions of it.
Ahh well there goes my theory, back to the drawing board.