More on the mobile ad front: The major portals (Google, Yahoo, and MSN) aim to generate billions of dollars in new revenue over the next decade by selling advertising on mobile phones, Bloomberg reports. But their biggest obstacle isn't each other.

"It's wireless carriers such as AT&T Inc. and Verizon Wireless, which have kept mobile Internet rates high while defending other revenue sources that the advertising may undermine."

There's been quite an undercurrent recently in the wireless industry that's pushing the carriers to open their networks and reduce meddling with mobile services.

"The carriers are too busy trying to protect the money they are making now to look at the next way to make money," said Chad Stoller, who heads the mobile practice at Organic, a San Francisco ad agency. Phone companies "want to control every aspect of the relationship between the consumer and the phone." That, in a nutshell, is the problem--and until it's resolved, a lot of these mobile ad campaigns and new services will continue to stagnate.

Google, Yahoo Clash With AT&T, Verizon on Mobile Ads (Update2) [Bloomberg]