• by Gavin O'Malley  @mp_gavin, May 23, 2008

Like a "dot-com" 10 years ago, a "social" foundation seems to be what attracts venture capital to startups these days. Indeed, makers of infectious widgets, viral content, and community-creating platforms are at the top of VC's watch lists.

The latest example of this trend is Flock, a social Web browser, which just completed a $15 million round of funding led by Fidelity Ventures.

"The browser is strategic because it enables nearly everything users do online," said Larry Cheng, Partner at Fidelity Ventures.

All previous investors including Bessemer Venture Partners, Catamount Ventures and Shasta Ventures--already responsible for more than $12 million--participated in this latest round.

The Flock browser is built on the open-source Mozilla Firefox code, and is connected to social online services like Twitter, MySpace, Facebook, and Flickr with features for users to broadcast messages to their networks.

"It just makes sharing incredibly simple, and lets you take friends along for the ride," said Shawn Hardin, CEO of Flock.

With a Flock browser, users can execute community-related activities like upload photos directly to Photobucket or Flickr, access news aggregation services, or use blogging tools.

The latest funding round will be used to expand Flock's business, including research and development, marketing and expansion into new global markets, according to Hardin.

"We're seeing more than half of our downloads abroad," he told Online Media Daily. The Redwood City, Calif.-based Flock was founded in 2005, but did not launch until November 2007. Since then, it has been downloaded nearly 4 million times, according to Hardin.

By contrast, Mozilla recently announced that its Firefox browser has been downloaded nearly 500 million times since its launch in late 2004. The Firefox browser has around 17% market share worldwide, and roughly 150 million active users.

Since the beginning of the year, Flock's user base is up by nearly 300%, while revenue is up 400%, Hardin added.

As with Firefox and other Web browsers, the company derives most of its revenue from search placement deals with search engines. Flock's main search partner is Yahoo.