It could be bandwidth issues at your end or an issue at the web sites you typically visit.
Try downloading something from Microsoft. I'm currently using Cox cable (Southern California), but there aren't many others nearby using cable modems, and although the stated download rate is 12 megabits per second, I've seen over 2 megabytes / second downloads from Microsoft, although Cox may be caching some of these (my last download was Virtual PC 2007 SP1 which wouldn't seem to be that popular), or there's some compression going on (2 megabytes would be 16 megabits per second), or Cox had yet again bumped up the speed (it's just a paramater in a cable modem set by the ISP via software commands). Note that Cox limits upload speed to about 10% of the download speed (to discourage people hosting servers).
If you're referring to lag in online gaming, it's the distance and number of nodes involved between you, the server, and/or other players. The time it takes for information to propagate isn't affected by bandwidth (if the information packets are relatively small). Satellites, being 22,000 miles up, add about 1/4 second of lag (22,000 miles x 2 / (186,000 miles / second), for each transfer of information.
The current limit for USA (DOCSIS 1.1 or 2.0) cable modems is 38.7 megabits / seconds download, 9 (DOCSIS 1.1) or 27 (DOCSIS 2.0) megabits / second upload. This would consume all of a 6 mhz channel on a cable. My cable modem supports 88mhz to 860mhz, being able to select 1 of up to 128 channels.