The short version is that videos will be throttled to 480p (DVD quality) on all Comcast mobile plans unless you pay extra, while Comcast's "unlimited" plan will limit mobile hotspot speeds to 600kbps. Only customers who pay by the gigabyte will get full-speed tethering, but the cost would add up quickly as Comcast charges $12 for each gigabyte.

Comcast last year began selling mobile plans with data, voice, and texting. Comcast doesn't operate its own cellular network, so it resells Verizon Wireless service.

Accroding to Ars Technica, the new speed limits could help Comcast save money on the reselling fees it pays Verizon. Comcast said it's making the changes "to help us maintain the low price point of Xfinity Mobile". While Comcast doesn't control the Verizon network and thus can't impose speed limits directly, Comcast told Ars that Verizon offers resellers an option to limit video resolution.

Comcast said that 480p "is consistent with standard unlimited plans across carriers" and that it's making the changes to bring Comcast's offerings in line with the rest of the industry. Verizon began throttling mobile video to 480p or 720p on smartphones last year -  the system limits the amount of bandwidth available to anything identified as a video. Carriers argue that many consumers can't tell the difference between 480p and higher quality on smartphone screens.

Comcast is trying to convince customers that the new speed limits will be good for them. The 480p video limit "can help you save money if you pay By the Gig" and it could help unlimited data customers stay under the 20GB throttling threshold, Comcast told customers: "At this speed, you'll conserve data so that it takes longer to reach the 20GB threshold, but you'll still be able to do many of the online activities you enjoy."

The only person who enjoys that sort of thing is a masochist.  Still nice to know that deregulation of the telcos is turning out so well for the Americian customer.