My answer on Quora:
It's a much more expensive proposition to stream to a set top box than it is to stream to the web. The technology is very wide and varied between the differing platforms, which takes up a lot of development resources. Typically, if you want to go to mainstream platforms (like the xBox or iOS), you've got to use a completely different streaming server solution, and all the live streaming platforms you mention are pretty in bed with the Flash Media Server suite.

Why aren't Ustream, Justin.tv, and Livestream making a push on set-top boxes?

I'm posting this here partially to test the integration between WordPress, and partially to put a pin into this topic. From a strategic position, at least on the surface, it seems like a pretty good idea to go for the living room if you're these guys, but there's a nuanced opinion in my mind forming around this that may explain the lack of live streaming presence in people's living rooms. So – more on this later. Probably.