You should worry if you intend to do the following things: An average Comcast customer uses two to three gigabytes of bandwidth a month, Comcast said. To reach the 250G-byte limit, a customer would have to do one of the following: send 50 million e-mails, download 62,500 songs or download 125 standard-definition movies, the company said in its announcement. comcast.com and networkworld.com