Two prominent Washington DC tech policy groups have asked the Federal Communications Commission to investigate Internet data caps in the US—with a special focus on AT&T.

New America Foundation and Public Knowledge say in a letter (PDF) that data caps aren't necessarily a problem, but that they do “carry the omnipresent temptation to act in anticompetitive monopolistic ways.”

Unlike competitors whose caps appear to be at least nominally linked to congestions during peak-use periods, AT&T seeks to convert caps into a profit center by charging additional fees to customers who exceed the cap. In addition to concerns raised by broadband caps generally, such a practice produces a perverse incentive for AT&T to avoid raising its caps even as its own capacity expands.

Comcast comes in for the same criticism. Its 250GB per month caps were introduced several years ago, and they have not increased since despite years of network upgrades that have dramatically boosted total capacity.

The fact that AT&T has just slapped a much smaller 150GB per month cap on its basic DSL subscribers seems strange to these groups, since the new cap is substantially lower than caps introduced years ago (and Comcast has been making plenty of cash since adopting the higher caps, so any economic arguments here are suspect).

The lower cap for DSL customers is especially worrying because one of the traditional selling points of DSL networks is that their dedicated circuit design helps to mitigate the impacts of heavy users on the rest of the network. Together, these caps suggest either that AT&T's current network compares poorly to that of a major competitor circa 2008 or that there are non-network-management motivations behind their creation.

Noting that moves to artificially limit Internet use would move against the FCC's own policy of encouraging broadband deployment and use, the two groups asked the agency to investigate data caps in the US. Specifically, they want to know if any ISP-offered services are excluded from the cap, how often the cap is enforced, how customers are warned about usage levels, and whether enforcement is related to network congestion.

In a less-than-intensely-competitive market providing a key piece of modern infrastructure, these are all excellent questions to ask. One might ask them much more sharply in places like Canada, where operators insist that their 2GB or 15GB or caps are absolutely necessary to make a profit.