I had a class in college that was (official or unoficially title... can't remember) Critical analyzation of the Bible...
There were atheists, christians, and other religions there (but mainly christians, then atheists). One of the girls in the class was extremely religious, saved herself for marriage, didn't cuss, etc, basically what's considered the stereotypical or idea christian.
One day in class, after reading the bible for the first time (well, on a "hey, it's ok to question!" reading, not a "you can read, but if you question, you're going to hell" reading like she was taught prior -- she made a point at the beggining of class, as did others, that it was taught to them that questioning the bible was blasphemous)... anyway.... she screamed "it's a lie, it's all a lie!" and ran out in tears. Didn't show up for classes in a while... the next week she was (literally) making out and having sex in a stairwell on the way to class, wearing clothing considered "slutish".
As the teacher said at the beginning of class, after it, it'll reinforce your opinions either for or aginst the bible, or, it'll change your opinion on it.
Her case was a huge shock to the class and the teacher (he actually was asking her questions the day that she ran out), and not common, but as a whole, the number of people thinking that the bible was true, without a doubt, was a lot less after the class than before it (many still believed in it, but as a neat collection of stories).
The reasoning that the professor had was simply that most of the people he encountered, had the bible, but never read it, and those that did, never thought of questioning it or anything like that. Along with the fact that many of the people in the class bought a Catholic bible, over the ones they had -- because not all of them had the same words, phrases, etc in the same places. And there were some instances (Genesis I believe...) that the stories were different, or had phrasing that gave opposite intrepretations. The professor himself actually believed in the bible, and was Catholic, so it's not like it was an atheist teaching or trying to "convert" people.