True.
In the context of this particular case, I was assuming that nothing the current size of YouTube could exist illegally, as that would imply that whatever authority was declaring them "illegal", but not capable of doing anything about it despite it nominally living in its jurisdiction, must be anemic and impotent to the point of being nearly non-existent.
There's already an underground proliferation of video sites, spreading copyrighted content out of the bounds of what the rightsholders want, so it's pretty much assured we'd end up with illegal alternatives. :)