This problem is of particular concern because there is hardly any competition in high-speed broadband services (speeds above 10 megabits per second). Some users have a choice between a cable company and a phone company. In many areas they have no choice. Caps should not just be a way for Internet providers to extract monopoly rents.

Data caps are a blunt way of managing broadband. Moving an extra gigabyte of data at off-peak times costs virtually nothing. Peak demand is the problem. Yet caps make no allowance for this. Moreover, there is no crunch in wireline broadband capacity, as there is in wireless. Internet providers must recoup substantial investments in their networks, but adding capacity is cheaper than putting up a network, and becoming cheaper all the time.

Caps can be used anticompetitively — to discourage the use of services that rival an Internet service provider’s in-house offerings. For instance, AT&T points out that Netflix hogs 30 percent of peak-hour Internet traffic in North America. Netflix also competes with television offerings on AT&T’s U-verse network. Watching TV on U-verse does not count against the data cap. Streaming Netflix does.

Caps are not universal in wireline broadband. Verizon and Time Warner Cable do not have them yet. (Time Warner Cable tried caps in 2008, but customers rebelled.)

Experts expect them to become more popular, and as they do, the Federal Communications Commission should seek to understand how effective they are at relieving congestion and what effect they have on services that rival Internet providers’ in-house offerings, like video. And it should keep an eye on whether caps respond to network efficiency gains and capacity increases. Caps must not impede development of broadband.