Believe it or not YouTube didn't exist when I started blogging five years ago. If I wanted to share something I saw on TV with you all I could do is either link to it or discuss it in whatever detail I could.
Now assuming someone else has posted some segment from TV, I can embed onto this blog. And this doesn't merely have to be YouTube. These days we also have the luxury of embedding from a variety of sources, especially if that clip is available from a major media outlet whether newspaper, TV or whatever. So it doesn't always have to be YouTube.
For example if I were to embed from the C-Span archives the program on the American Presidents I can do that here. Now be prepared to watch a program in excess of 2 or 3 hours.
Of course not all we see on YouTube needs to be that serious. People have become "famous" because people may have created some mindnumbing entertainment. There doesn't have to be any rhyme or reason for it, but it captures people's attention for the moment.
Perhaps that's the revolution of YouTube.