It's well known that some ISPs will cancel a customer's account or otherwise restrict them if that person excessively uses up bandwidth. A rather draconian measure, but I'd rather have someone tell me I'm downloading too much or simply cut me off than spring charges on me for using too much. That's what it looks like AT&T is considering, with some users being charged for going over a monthly allotment.
What the allotment is, what they would charge or even if they are doing more than just considering the idea isn't known. It wouldn't be surprising, as another ISP recently began experimenting with this as well. Earlier this year, Time Warner launched a pilot program in which they charge heavy users for their transgressions, with prices as high as $1 per gigabyte. The nature of the Internet is changing. Streaming music, streaming video and a lot of other newer content is available, increasingly moreso year after year. These ISPs seem willing to offload the cost onto the customer, rather than analyzing how their networks could be improved.
A spokesperson for AT&T brought out that a minority of their customers, 5%, consume about 46% of the amount of bandwidth used.