According to iPhone blogging site iPhonematters.com, AT&T is considering imposing a cap on data access for mobile devices of up to 5 GB.
The site says the cap is not meant to force customers into paying penalty fees, but instead to warn them of server overloads at the carrier. Text messaging would be counted separately from the capped data.
The post also said that if the cap is imposed, data plans at AT&T should drop down to $30, and that these changes could be announced in a few weeks.