Some people here are ditching it... I wouldn't call it "common" though. I know for me, ditching a landline's a virtual impossibility. Maybe it's the topography of Pittsburgh, not really sure, but I get bad signal at my girlfriend's house, as well as my own house. Neither is reliable, even through Verizon.
I don't honestly know anyone personally who has ditched their cable completely... Some have I guess, but nobody I'm friends with of any age. From what I've read, it's possible, but takes some work and you can't get HBO, etc. And I watch a lot of HBO's series.