The Associated Press' Dave Carpenter today looks at the marketing potential for SMS or mobile text messaging.

"From fast-food chains to carmakers to consumer goods manufacturers and sports franchises, more and more companies are adopting text messaging as a way to target consumers on the move," Carpenter writes.

Frost & Sullivan analyst Gerry Purdy says it's a trend ready to explode. "Probably the most important medium for advertising in the 21st century is going to be the cell phone, not print media, not billboards," he says.

The Yankee Group says more than 95 million Americans are active text messagers.

The biggest challenge to using text messages for marketing, Carpenter suggests, is the fact that most U.S. cellular carriers charge for both outgoing and incoming messages. When a consumer is being charged for messages, it's less likely that they'll opt in to receive ads.

"Verizon Wireless says marketers have shown tremendous interest in arranging text-messaging campaigns where recipients wouldn't be charged, though no deals have been cut as yet," Carpenter writes.