This idea comes up in a Slate review of Daveed Gartenstein-Ross' book, My Year Inside Radical Islam:
While working at the Al-Haramain Islamic Foundation, Gartenstein-Ross adopts some conservative Muslim practices, including a few advocated by the puritanical Salafi school of thought. He grows a beard; wears a kufi, or skullcap; refrains from praying together with or shaking the hands of women; avoids contact with dogs; rolls his pants above his ankles when he prays; and throws away his music collection. But he also dates a Christian woman, to whom he proposes without asking her to convert. And I never caught mention of him requesting halal food in his parents' home, where he was living during his internship. His new religious behaviors were surely meaningful and important to him, but they hardly meet the prevailing American definition of a "radicalized Muslim" as someone who retreats from secular society, advocates a nation governed by Muslim law, and resorts to violence against those who would thwart such plans. And if that definition truly is wildly off-base, Gartenstein-Ross does nothing in the book to challenge it with an alternative.
He does undertake one genuinely "radical" religious action: Midway through his internship, he begins to pray daily for the mujahideen in Chechnya. Outside of his conscience, though, the closest he comes to doing anything radical, illegal, or related to terrorism is when he nearly meets at the airport a man he later learns was trying to procure money for al-Qaida. To repeat -- he almost met someone who he had no idea was in the country to do evil. If this is the experience of a young Westerner who's been drawn into the world of radical Islam, then perhaps we have less to worry about than we thought.
But Gartenstein-Ross isn't John Walker Lindh, interrupted. His is merely the tale of a confused, suggestible kid with what comes off as an unquenchable need for acceptance within whatever community he happens to find himself. For conservative commentators to suggest that this is a cautionary, inspirational tale is off the mark. Time and again, Gartenstein-Ross reports examples that we're supposed to react to with the horrified feeling that he's being brainwashed. Instead, though, they come across as confusing behavior by someone undergoing a spiritual crisis and who seems almost eager to back down from beliefs he once held dear.
To be fair, I haven't read his book, but it certainly sounds like Gartenstein-Ross fell in with a group of fundamentalist Muslims, then decided that their belief system wasn't for him. This is not to say that it's not an interesting subject, the experience of a convert, and his decision to go back on his conversion (a process that took two years from beginning to end). But what it is not, is a look at Islamic terrorism, which is really where the book market seems to be these days.
So while it might be interesting to read an account of someone who was "born again" into one of the churches that we see in Jesus Camp, it wouldn't necessarily help us to understand what makes a Christian or Muslim fundamentalist move from more or less extreme religious beliefs to religious violence.