The most consistent rationale for ISPs to throttle p2p applications or charge by the byte is that a small minority of users drain a vastly disproportionate amount of bandwidth, like the planet-raping aliens in Independence Day. Om Malik pulls a few of these numbers out of Arbor Networks' CTO, who develops all the traffic management tools your ISP probably uses, so while there's a conflict of interest (portents of internet doom sell more stuff) they have the data. Ten percent of subscribers consume 80 percent of bandwidth, a super-leeching 0.5 percent swallow 40 percent of bandwidth, and the rest like your mum, 80 percent, sip less than 10 percent. But p2p isn't the culprit.
No, p2p is no longer the single biggest traffic whore, responsible for only 20 percent of total traffic. It's streaming video, like YouTube and Hulu, which is now 50 percent of total traffic. During peak congestion—the times when Comcast will slow you down for hitting the pipe too hard—70 percent of it is http.
Which explains Comcast's flip on network management and why it's a total smokescreen. P2P is no longer the number one leech on networks, it's streaming video across regular old http. So they don't need to throttle p2p exclusively anymore—they need to slow the whole pipe down, hence the new "protocol agnostic" scheme. But they can look good showing off how much they love p2p. It remains to be seen how much of it the FCC will eat up. [GigaOM]