"The mistake we've been making in evaluating mass-market first-mover YouTube has been in thinking that Google-like dominance is possible in the content arena. But, of course, that's as daft as thinking that we'd always need America Online."
And that's the guts of it, as summarized by Simon Dumenco at Advertising Age: As we all become more comfortable with using and sharing video online, YouTube will be less and less relevant, eventually trying (and failing) to catch up with one of a million sites that do the same thing they do, only better.
Related story here, via Phoenix New Times, re: the predicted demise (or dethroning, at least) of MySpace.
Something to consider next time you're searching for kitten videos.