Industry watchers say Verizon has a clinch on the C block while another carrier, perhaps Alltel (nyse: AT - news - people ), likely has won one or two licenses.

FORBES: Google Likely Out, And Happy

In that scenario, says Free World Dialup's Pulver, a carrier could block service and effectively make its own VoIP product the only available option.

FORBES

Does the President support a plan that, according to critics, would allow a carrier such as Verizon or any other carrier to block users from using a service that competes with a service they offer?

WHITEHOUSE: Press Briefing

The carriers will block listed phones from accessing carrier networks for voice and data service.

WSJ: U.S. Government, Carriers Plan a National Database of Stolen Cellphones

Most iPads rely on Wi-Fi for connectivity, rather than a carrier network, so carriers can't block them.

WSJ: How to Fight iPhone Theft

The formerly state-owned carrier, Varig, is badly run, bankrupt and on the auction block.

FORBES: Stepping South Of The Border

Yes, Android might be "open" in the sense that the source code is available, but there's no doubt Google's wielded incredible power over the platform by restricting access to Market and its own apps -- power that hasn't been used to prevent carrier-mandated bloatware or poorly-done manufacturer skinning, but has instead apparently been used to block legitimate competitors like Skyhook from doing business.

ENGADGET: Skyhook: Google forced Motorola to drop our location service, delay the Droid X