Marshall doesn't think buyers of the new Kindle will suffer for using AT&T's network, which has come under some criticism for not keeping up with exploding data demand from the iPhone. As AT&T rolls out 7.2M bps (bit-per-second) HSPA, it will close the gap with EV-DO networks and have a smooth migration path to LTE in 2011, he said.

Sprint was disappointed at Amazon's move to AT&T but sees rapid growth and high volume ahead in all types of M2M services on all networks, said Wayne Ward, vice president of emerging solutions at the carrier. For example, Sprint powers the recently introduced Little Buddy Child Tracker, a GPS tracking device from Best Buy's Insignia brand.

"It's really a wide-open landscape right now," Ward said. By contrast, the traditional cellular business has reached maturity in the U.S. as most residents already have mobile phones and are simply switching among carriers, he said. M2M uses of wireless, such as meter-reading, represent solid business opportunities. "These things seem to stay embedded for quite a long time," Ward said.

Ward is also optimistic about WiMax, saying there are about 500 commercial deployments of the technology under way in 130 countries. The first commercial LTE services are forecast to appear next year.

Still, a fast-moving business can be full of uncertainties, as demonstrated by Amazon's switch.