I don't have one either. As someone else mentioned, most shows can be either streamed or downloaded for free, and if I want to catch a game I can visit a friend or head to a bar. When I'm at my parents' house or something and have access to a tv, there's usually nothing on. I like having shows online where I can watch them whenever I want.
I do spend too much time on the web, but I guess I learn more here than I do watching tv. Cable is way too expensive anyway, especially since I live alone.