Why install a weird temperamental app when you can just stream video from Twitch (Amazon) or YouTube or Facebook? They've all invested tens of billions in networking infrastructure and have the necessary advertising structures to recoup the costs.
Streaming bandwidth is super pricey, and the money is enough to really matter. Even a startup can easily get to five or six figure expenses. Bittorrent Live gets that right.
However transcoding is critical, given that every OS and browser has its own format quirks. BT Live can't remotely do this.
Check out Zencoder for the real competition.
Maybe BT Live will find a niche with use cases that just produce no money at all, or where servers get shut down for political reasons. Marches, samizdat, and, uh, questionable copyright.
On a personal note, it's great to see the old decentralization crew on this thread.
1) overall user experience including seemless play and video quality
2) customer support burden
During a huge scale live event you can't afford to have more than a very small fraction of the users experiencing technical problems.