A Comcast insider tells me the company is considering implementing very clear monthly caps, and may begin charging overage fees for customers who cross them. While still in the early stages of development, the plan -- as it stands now -- would work like this: all users get a 250GB per month cap. Users would get one free "slip up" in a twelve month period, after which users would pay a $15 charge for each 10 GB over the cap they travel. According to the source, the plan has "a lot of momentum behind it," and initial testing is slated to begin in a month or two.
As a few of you may have noticed, Comcast received a public relations beating and is being investigated by the FCC for their use of Sandvine gear to throttle upstream P2P traffic. This practice of using forged TCP packets to "break" BitTorrent connections. Comcast also boots high consumption users from their network for crossing an invisible consumption threshold.