The register has a story on an analyst's estimate (whatever that's worth these days) that youtube will be losing close to half a billion $ this year. They take this as an indication that the ad model is not working. After discussing two reasons why this might be the case -- either Google doesn't know how to do it (unlikely) or the model is fundamentally broken (more likely) -- they come up with an option for Google to make money out of youtube.
Of course, there's a third option for YouTube. Its parent company - whoever that may be - may want to cross-subsidize the operation in the hope that will drive traffic elsewhere on the site. Don't laugh - that's exactly what Google's new music service in China does. Google China pays rightsholders much more than 0.22p per song - about ten times as much, according to industry estimates. As Baidu has shown, music drives enormous traffic to the rest of the operation.
See also Ars Technica's article on the same subject.
Update (14.04.): On the other hand, artists are demanding that Youtube increases it's payment to them.
Update II (15.04). A detailed breakdown of revenue and costs. The most interesting figure is the amount given to independent creators through it's revenue sharing program.
Revenue share: If you provide videos to Google and join its revenue sharing program, then you get a commission if ads are shown alongside your content. Credit Suisse estimates that YouTube will "share" away $24 million this year -- $66,000 per day.