This should not be downvoted. YouTube does not have a viable competitor because serving video is incredibly expensive.
Edit: This is being downvoted as well. Downvoted is for off-topic or inflammatory comments, not for comments you disagree with. If you disagree, leave a comment and explain why!
Is that true? What about Vimeo, Dailymotion, and the countless streaming sites which pop up to serve pirated content?
I don't doubt serving video to an audience as large as YouTube's is very expensive, but then with an audience as large as YouTube's there's a lot of money to be made. Bandwidth cost scales with views.
Surely YouTube's advantage is a network effect. They make it easy and quick to upload videos which then have the potential to be viewed millions or billions of times. Plenty of people use Vimeo, but there's not the same potential for virality.