Celebrity-focused social media management platform WhoSay has raised $12 million in Series C financing led by Comcast Ventures, with participation from existing investors Greylock Partners, Amazon and High Peaks Ventures participating, as well as Chinese social media portal Tencent.

WhoSay was launched in 2010 within CAA, a talent mega-agency, to give the firm’s celebrity clients more control over how their photos were being used online. The platform has grown significantly in the four years since to support more than 1,000 members, most of which are non-CAA clients, who have more than one billion combined social media connections.

“WhoSay has become the dominant content management platform for the world’s most influential personalities,” says Comcast Ventures partner Sam Landman. “By helping high profile talent efficiently and safely connect with fans through both social and mainstream media, WhoSay has built a unique and valuable asset.”

It’s common to see tweets sent by celebrities like Tom Hanks, Steven Tyler, and Ellen DeGeneres marked as “via WhoSay.”  Analogous to a “HootSuite for the stars,” WhoSay allows artists and athletes to engage directly with fans by sharing media through a variety of social networks including Facebook, Twitter, Tumblr, YouTube, and Tencent. The company also has traditional media partnerships with Viacom/MTV Networks, the AP, and Yahoo!.

CEO Steve Ellis brings a strong background in content rights management to WhoSay, having served as founder and CEO of music-licensing business Pump Audio, which he sold to Getty Images in 2007. One of the largest value propositions of his new service is enabling stars to control and eventually monetize photos and videos they post to their networks.

Ellis explains that without a service like the one his company provides, stars create enormous value in the media space, but don’t get sufficient return return for that value. Additionally, stars need professional help in managing their online presence in a rapidly changing environment that shows no signs of slowing.

“This is a fast changing, fast paced situation, and we believe that our service to our clients is help them manage and optimize this environment without dealing with the underlying technology,” says the CEO in reference to the ever-changing smorgasbord of social media platforms.

Much like WhoSay investor Amazon is a media and technology company — “maybe the most effective direct to fan commerce and media company on the planet at this point,” according to Ellis — WhoSay is looking to merge elements of media and elements of commerce going forward. In addition to serving as a model for WhoSay, there seems to be a natural partnership to be formed between the startup and Amazon-owned hollywood database IMDB.

Ellis’ vision for the future of WhoSay and his plan for the newly raised financing is to build additional fan experiences and drive further engagement. Until now, the company has mostly focused on the celebrity’s experience. In the future, WhoSay will capitalize on the content it’s pushing to create personalized user experience for fans on the other side.

“If you want a vision of where that goes, you don’t need to look any further than the print version of people magazine and what goes into there,” he says. In other words, we have the content and we plan to use it. WhoSay has the ability to create personalized digests of celebrity content delivered directly to their fans, possibly monetized with ads (or even subscriptions). With more than one billion combined followers, Whosay has a larger audience than any glossy celebrity magazine.

The company was founded within CAA’s Los Angeles offices, which offered an invaluable access and perspective while also helping to acquire its impressive list of celeb clients. The company has since moved its headquarters to New York. The move was driven by the fact that Ellis’ previous company was based in NY and that he brought aboard much of the same team when launching WhoSay. Additionally, many of the leading media brands and ad agencies are based there.

WhoSay plans to continue its push toward international expansion, highlighted by the new Tencent partnership. “Our mission is to support our clients in directly connecting with their fans wherever they are,” says Ellis. “We believe that our partners [Tencent, Comcast, Viacom] help us do that in a major way. [New addition] Comcast Ventures is a partner with deep media experience and a great track record of success… and they add a vast knowledge of the marketplace in both mainstream and digital media.”