I don't think it'll be the undoing of youtube - not at all. Youtube offers much to their audience, this certainly won't dramatically change their business. It does however give any competitor a much better standing to compete against youtube, giving the competitor relevance and a bucket load of traffic from consumers seeking desirable content. (The top 10 searches every year involve one or more music celebrities.)

It'll be interesting how it plays out anyway, now that google has announced it will discontinue video search altogether (in favour of youtube only.)