All of these services ask me to think about what I want to watch. But there's this thing that we all do, and I absolutely think there isn't a single person that doesn't do this, and it's called "channel surfing". You just flip and flip and flip to see if there's something more interesting than you're currently watching, or you've just finished watching a program and you want to explore your options.
Stumbleupon provides exactly this, but much more. Stumbleupon is purpose-built specifically for boredom, and over time tailors itself to you. Next, next, next, ohh that's cool, next, next, next. That's exactly what I want from a TV experience. Additionally, I'd be able to save and share with friends.
An example of how this feature would differentiate itself from current methods is, I like a lot of TED videos, but there's also a lot I find incredibly boring. With current interfaces, I have to click a TED category and then sift through all of their offerings. And how the heck would I even know if I'll like something until I play it? Blegh! The Stumbleupon feature would know what type of content I like, and would be able to pull out TED videos that it thinks I would find interesting, and all I would have had to do was click "Next", and it would eventually be presented to me.
That's all I got to say. Add a dang Stumbleupon feature, and an internet-tv box will be MONEY.