One service provider, Clearwire, is already mobile data service for about $30 per month (with a usage cap of 2GB) and what it calls "unlimited" mobile data for $40. But its WiMax network is only commercially available in four major cities, with 10 smaller markets going live next month. To get service beyond those areas, traveling users need a dual-mode 3G/WiMax modem and an $80-per-month service.

Leichtman Research reported that the major U.S. carriers and cable operators gained only 634,000 net new subscribers in the second quarter of this year, the lowest number since the company began tracking broadband growth eight years ago. Together, the service providers only added 71 percent as many new subscribers as they did in the second quarter of 2008.

Part of this drop may have been caused by the recession, but mostly it reflects the increasing saturation of the U.S. broadband market, said Bruce Leichtman, principal analyst at Leichtman Research. The second quarter historically has been the weakest of the year for broadband additions, but comparative results from a year earlier have been similar in other recent quarters, he said.

"That's about the trend we're at, in overall net adds," Leichtman said.

Only about two-thirds of U.S. households have high-speed Internet access, Leichtman said, even though his company's phone surveys show only that 3 percent of Americans say they can't get it. One reason home broadband penetration may be topping out at such a seemingly low percentage is that only 86 percent of U.S. households even have a computer, Leichtman said.