At a time when ad networks were being tapped up by the likes of Apple and Google for hundreds of millions of dollars, many saw Millennial Media's purchase of analytics firm TapMetrics in February as a move to hold on to its independence.

News that Millennial has secured $27.5 million in a round of funding – bringing total equity funding to $65 million – could be taken in much the same vein.

Aiding expansionMillennial itself says the new funds – injected by Bessemer Venture Partners, Columbia Capital, Charles River Ventures and New Enterprise Associates – will be used for further growth, the company openly touting further acquisitions in 2011.

Not that 2010 was without its own reward. According to the firm's figures, annual revenues trippled across the course of the year, with the ad network now reaching 85 percent of mobile web users in the US.

Furthermore, Millennial now reaches out to 250 countries, serving 17 billion ad impressions a month.

"We made significant investments in our technology platform, which supports not only our own mobile ad networks, but also is the platform behind mobile advertising programs operated by many of our partners," said president and CEO Paul Palmieri.

"Following on our successful acquisition and integration of TapMetrics last year, we plan to aggressively pursue these types of growth opportunities as they arise in 2011."

[source: Millennial Media]