Verizon Wireless yesterday announced a new $100-a-month plan with unlimited calling - and in doing so, the company appears to have set off a pricing war among U.S. carriers. AT&T and T-Mobile matched Verizon's plan within hours, and Sprint is rumored to be planning to do so soon.

"Analysts say [Sprint] could be considering an unlimited calling plan for as low as $60 a month to stem customer defections," writes Reuters' Sinead Carew.

"The wide gap could force other carriers to drop their own prices... potentially leading to a succession of rate cuts or feature bundles from rivals concerned about losing customers to Sprint," Electronista writes.

That, of course, would be good news for consumers, but bad news for carriers. "Worries about a price war have lopped 11% off of AT&T shares and 10% off Verizon shares in the last two days," notes TheStreet's Robert Holmes. "Sprint is down 8% over the previous two sessions."

"This could get really ugly and really fun," the AndroidGuys write. "What a great time to be a consumer, eh?"

More here from the Washington Post ... more here from BetaNews ... more here from ZDNet ... more here from BusinessWeek ... more here from TMCnet ... more here from the AP ... and Verizon's press release is here.