I think Comcast has a 1TB per month limit in many places.
I live by myself and use around 400GB. I could easily see 2+ person household going over that limit if you stream a lot of video. That's where the vast majority of my data use comes from. I don't torrent from home, I have a seedbox in Europe that handles my torrents. If I torrented from home I might even go over 1TB by myself!