Content from NBC and CBS is among the most popular with viewers of mobile video, with many tuning in to watch hour-long dramas — a format that initially thought to be unwieldy and unpopular with mobile viewers, reports MediaBuyerPlanner.

According to Nielsen, NBC.com draws the largest audience to mobile, generating 1.8 million mobile video streams. Of those, 1.3 million were for full episodes of shows like Heroes and The Office.

"Long-form is doing better for us than short form, and yes, we're surprised. But we shouldn't be surprised, since we had the same thought online, and that's proven not to be true," says Steve Andrade, general manager of NBC.com.

Part of the reason traditional shows are popular is because they're familiar. Made-for-mobile shows, like those CBS has had in development, are hard to find because mobile web users are less inclined to search aimlessly, especially for unfamiliar forms of entertainment. Still, CBS continues to produce original mobile series, and has scored with such shorts as Daily Delivery, which offers short Hollywood news segments.

Nielsen estimates that 10.3 million mobile phone subscribers - or 5% of the cell phone population - access video via their phone each month. M:Metrics’ most recent survey shows that just 7.5 million users watched video in a given month.

NBCU is experimenting with a metric that will measure audiences across television, online, mobile devices and video on demand. It began offering the Total Audience Measurement Index (or TAMI) beginning with its 17 days of Summer Olympics coverage.

Mobile internet penetration is expected to soar this year, according to comScore: As smartphones (including the iPhone) continue to drop in price, and new entrants impress consumers, 2009 is expected to be another record-breaking year for the mobile internet, comScore said. Mobile internet penetration and engagement will continue to soar, providing more opportunities for advertisers and marketers.

A recent Cisco survey found nearly one-quarter of Americans watch videos from mobile units.