FYI I'm in Canada and use Canadian Netflix. I have a 175GB cap on my cable internet (it's the biggest I could buy). This month I was sitting at about 120GB transfer with average netflix watching (several TV episodes a night and 1-2 movies a week), with about a week left.

Then I acidentally left the live.twit.tv stream on for about 12 hours. I haven't checked, but I expect to either have to heavily conserve bandwidth until my next bill, or get a friendly letter from my ISP. Offsite backups like carbonite or mozy are totally out of the question obviously. I had planned on downloading MS Server 2011, but I'll have to put that off until the next billing cycle too. I also rent and buy movies and TV shows off of itunes, but I have to balance that and my netflix watching so I don't go over.

Everything I do is 100% legal, yet without vigilance I could easily blow through my cap within two weeks. The phone company offers a slightly higher cap (you can get up to 250GB) but it's much slower. Welcome to life in Canada...