There are no download limits for Comcast. Our contract is unlimited download but yes they do reserve the right to discontinue service or block net but they don't. I have downloaded over 100 GB in a month (Legally) and nothing was said. All of the games I buy are D2D. Also I have 4 computers running off of my net. 2 Business computers and 2 personal. Our net is not lightly used to say the least.
Comcast I will say has been much more lenient with me, but they do have limits in their data, you just need to read the real real fine print in your contract. However I can say I am also doing well over 100GB a month (um I guess I'll say legally to be part of the trend) and they have only suggested that I get a T1 or T3 line for the improved data rate, and the static IP, though they have yet to push me off their normal Cable service.
There was a daily tech article about this awhile ago actually.
Cheers
Cameron
EDIT: Yup and here it is http://www.dailytech.com/No+Usage+Limit ... le8901.htm Officially Comcast has a 2GB per month bandwidth limit on its subscribers because they figure that with leagle downloading you aren't going to exceed that, however with all the lawsuits flying over the P2P throttles that US ISPs are placing on their subscribers ISPs have been very careful about saying anything to anyone.