AT&T chief tech officer John Donovan has told Wired that they're going to test bandwidth caps in the fall, making them the third of the four major ISPs to do so. (Verizon stands alone, but for how long?) He lays out the familiar rationale, a small group of users (5 percent) pillage the network (40 percent) and they've got to stop them. But then he slips what's probably the real reason they've moving to caps: "Traffic on our backbone is growing 60 percent per year, but our revenue is not."
It is more or less accepted that a minority of users use disproportionate of bandwidth, but what they're using it for is changing. It's increasingly video, not BitTorrent. The whole pro-BitTorrent thing is a smokescreen, because BitTorrent is less and less of an issue—video, and increasingly, HD video will be the real one. (Along with any number of other increasingly bandwidth-intensive apps.) And it'll be more and more competitive with providers' TV offerings—we've already seen Time Warner cry about it. But there's no legitimate way to block it and protect their content.
They can, however, make it more expensive for you to download with bandwidth caps (which is conveniently net neutral). And that's what I think this is partially about—protecting their TV business, not just curbing voracious bandwidth appetites. Regardless of the motivations, it's definitely coming. Comcast's tests will probably start soon, Time Warner's are already underway and regional ISPs have been doing it for a while. It's looking very much like the future of broadband here.