The audience figures include video viewed directly on wireless carriers' decks or sent by friends or family members as of Aug. 31. Viewership for video delivered on-deck increased 28% since January to 2.7 milion. The increasing numbers are a promising sign for mobile publishers and advertisers, say MMetrics analysts.

"If operators and handset manufacturers or publishers are hoping to see a mobile video take off, this is good news," says Mark Donovan, senior analyst at MMetrics. For advertisers, he acknowledges that the audience is still small compared to the Internet and TV.

Video watchers represent only a tiny fraction of all cell phone subscribers in the U.S. Those who watched over-the-air mobile TV broadcasts and/or video clips at least once a week amounted to less than one percent. Those tuning in monthly represented 3.7%. Similarly, only 3.2% of mobile subscribers watched videos sent by friends or family.

Almost 30% of U.S. mobile phone users own video-capable mobile phones, according to a study last year by the NPD Group and the Mobile Marketing Association.

Donovan noted, however, that mobile advertising is driven by qualitative as well as quantitative factors. "Not only can you deliver messages and offer promotions to people on mobile phones, but they have a mechanism right there to respond whether click-to-call or a short code number." he says.

Market researcher eMarketer predicts that U.S. mobile ad spending overall will grow from an estimated $421 in 2006 to $4.8 billion in 2011. Mobile marketing and content tied to broadcast TV also will climb to nearly $1 billion within three years.

Boosting demand for carriers' on-deck programming have been aggressive promotion, wider distribution of 3G phones, and more compelling content.

"Sprint's performance is particularly noteworthy, as the carrier's subscribers comprise more than 36 percent of the total audience for programmed video," says Seamus McAteer, chief product architect and senior analyst at MMetrics.

Overall, text-messaging remained by far the most popular mobile activity among U.S. subscribers, with 43% thumbing away on keypads. A distant runner-up was photo-messaging at 19%, followed by e-mail and instant messaging, each at about 9%.

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