Comcast has implemented a 250gb per month limit on the amount one can transfer over their high speed connection.
Go to https://customer.comcast.com/Secure/UsageMeterDetail.aspx, login and you will see your usage history.
Comcast has had a usage limit since about October 2008, but without a usage meter, I always felt like the Comcast usage police might come knocking at my door. Having a usage meter is a step in the right direction. I wish they would add some kind of alert system, that I could use to signal to me when usage goes over by a certain amount (that way I can keep track of my data usage and if any pirate is trying to steal my bandwidth).
Here is what data usage meter looks like.