• by Gavin O'Malley  @mp_gavin, June 5, 2013

So much for CBS Interactive’s exclusive ad sales pact with video platform Twitch.TV. Just months after the deal was done, Twitch -- which specializes in live footage of video games being played -- is dropping CBSi to form its own internal ad sales unit.

Jonathan Simpson-Bint, chief revenue officer at Twitch, said the partners will remain close. “They’ve actually been very understanding, and we’ll continue to work together on advertising and content,” Simpson-Bint said of CBSi. “We still need to build our national advertising business, and CBSi is a significant content provider."

At launch, the Twitch Media Group boasts a network of some 600,000 “broadcasters,” which attracted an audience of 35 million unique visitors in May.

To support its new Media Group, Twitch has hired several sales executives, including Kym Nelson -- former vice president of West Coast sales at IGN Entertainment -- who joins as senior vice president of sales.

Andy Swanson -- most recently vice president of digital business development at GameFly -- has been named vice president of sales at Twitch, while Christina Grushkin -- who previously served as senior sales manager at Future US -- is joining the team as senior sales manager.

As for Twitch’s sales pitch, Simpson-Bint said it’s all about live video, and young users' zeal for gaming. “A big part of what we’ll be doing is custom solutions, and figuring out how advertisers can take advantage of our live audiences,” he explained.

As the father of a 16-year-old boy, Simpson-Bint spoke from experience when he said: “Watching video games is now a serious form of entertainment.”

Letting their consoles cool off, a full 72% of U.S. gamers now play games online -- up 5 percentage points year-over-year -- according to recent data from NPD Research.

And all that traffic is attracting the attention of the Web’s biggest ad servers. Even Google is developing a video game strategy, and recently hired gaming guru Noah Falstein to spearhead the effort as its chief game designer.

Late last year, Twitch raised $15 million to continue scaling its online video platform. This latest round was led by Bessemer Venture Partners, along with participation from Alsop Louie Partners and Draper Associates.