PVRBlog links to a Steven Levy piece on TV watching habits:

The result may be that when all the time-shifting and space-shifting is accounted for, most people will watch the same stuff by the same creators. In fact, even with today's relative abundance, most people stick to only a few channels. According to Nielsen Media Research, households that receive about 60 channels usually watch only 15. Households whose systems can receive 96 channels (around the national average) actually watch... 15. What's more, a recent study conducted at the UPenn Annenberg School for Communications showed that when people were offered more programming choices, they stuck to fewer selections—and, alarmingly, watched fewer news shows.

Well, the thing is that those "15 channels" vary a lot, I think. While each of us may only watch a small set of the available stuff, I'd bet that the small set varies quite a bit over different households (and varies quite a bit over time depending on the household demographics, as well). For instance - we watch a lot less Nickleodeon now that our daughter is 11 than we did when she was 5.

The hard bit of market research here is figuring out what part of the target audience any particular household is in.