Pharyngula mentions a letter in Science which talks about how a creationist motivated an unmotivated high school student to become an evolutionary biologist. This struck a chord with me: it was creationism that turned me into an atheist.
There was a time during my teenage years when I was a Christian. I tended to take things in the Bible literally, although I did allow for words being mistranslated or fudged. As I always had an interest in science, I even tried fitting the known history of the universe to the first creation narrative in Genesis. This all changed when I read Henry Morris' Scientific Creationism. Even to my teenage mind, so much of the book was just so obviously wrong that it finally occurred to me that not everything anyone says is the truth. This made me dig into the evidence supporting religions, and I found out that religions ultimately had nothing more than just "someone said so" backing them up, which was rather pathetic as evidence.
While I doubt I would have grown up to be a fire-breathing fundamentalist Christian, I think I would have been a liberal Christian or a deist if it were not for creationism. The funny thing is that I had never read any atheist literature nor heard any arguments advocating atheism until many years after I had become an atheist. Until some time during university, I had not even really known what "atheist" meant besides that it was a type of person some people disliked. Incidentally, this is why I prefer saying that I am not religious, which is clear in its meaning, rather than that I am an atheist, which might face the sort of ignorance I once had.
The moral of the story could be: If you lie for Jesus, some people might realize that Jesus is a lie.