If you count my provider's on demand TV streaming service (which it treats as seperate) it's over 100GB a month. Love my 30Mb unlimited internet!
I don't have cable, I have netflix. Also, I keep the TV on almost 24/7 for background noise.
I remember butting up against Comcast's 250 gb limit quite often when I was single (lots of HD Netflix and other types of downloads). Probably around 50 gb per month now.