Bart Ehrman is an American New Testament scholar and textual critic of early Christianity. He is the James A. Gray Distinguished Professor and chair of the Department of Religious Studies at the University of North Carolina at Chapel Hill.
According to wikipedia,
Ehrman became an Evangelical Christian as a teen. His desire to understand the original words of the Bible led him to the study of ancient languages and to textual criticism, to which he attributes the inspiration for an ongoing critical exploration of the basis of his own religious beliefs, which in turn gradually led to the questioning of his faith in the Bible as the inerrant, unchanging word of God. He now considers himself an agnostic.
He is the author of or has contributed to more than 20 books. Last year, he published another book called Jesus, Interrupted: Revealing the Hidden Contradictions in the Bible (And Why We Don't Know About Them).
Here's Ehrman being interviewed by Terry Gross on NPR's "Fresh Air".
Part1 of 4: http://www.youtube.com/watch?v=2HnntlAd2x8
Part 2 of 4: http://www.youtube.com/watch?v=UoQ54p6j6bc
Part 3 of 4: http://www.youtube.com/watch?v=Sl5K5Vj8Aog
Part 4 of 4: http://www.youtube.com/watch?v=NRtS81RnU2M