I love this post from Engadget. It's about YouTube and its costs and profitability. Engadget estimates that YouTube probably pays about a million a month in broadband. Given that it has recent funding of about $8 million, it's only bought itself the summer to show that it can profit.
Engadget traces the history of sites that start with free to prove the worth, and then migrate to models that are substantiated by ads or charge visitors. Certainly the former makes more sense since I don't see us soon paying another monthly fee (beyond broadband, cell, cable TV, etc.).