In "What is Islam?," a modestly dressed young woman sits in what appears to be a home office, with a computer, some shelves of books and a small American flag, describing the basic tenets of her faith and defending it against claims that it foments or tolerates terrorism. Laura, a Muslim convert who lives in Virginia Beach, Va., with her husband and twin boys, does not hold a paper Koran, but refers frequently to a copy on her laptop. "I hope to do whatever I can to promote Islam for the sake of Allah," the native Coloradan writes on her YouTube bio. Her videos are the epitome of plain, and yet, in a sign that some users are approaching YouTube as though it were Wikipedia, Laura's primer on Islam has drawn more than 368,000 hits and some 9,300 comments.