While I admire what justin.tv is doing, I think that in a way it's arrogant of the "Web 2.0"/Silicon Valley community to dismiss TV so quickly. Silicon Valley and the kinds of people who are adopting justin.tv are not the people who are watching TV in droves right now. I seriously doubt justin.tv commands the viewership in the tens or hundreds of millions that normal television does at its peak.
The people watching Justin.TV are not sophisticated Silicon Valley early adopters, believe me. And while nothing streamed online has the numbers of TV yet, I believe Justin.TV's numbers are as big as anything else online.
It's doing exactly what Stage6 did. Stage6 had amazing growth. The problem was that it was entirely fueled by the fact that they were hosting high quality pirated content. It's like standing on a street corner and handing out DVD rips of the latest movies for free. Of course you're going to be popular. Anyone with the balls and money to blow could do it, but why would they? It's a total gamble that you're going to sell the company before you get sued out of business.