Millennial Media has seen tremendous growth in the past few months, and it’s getting closer and closer to going public. The large, independent mobile ad network is reportedly in talks with banks. According to one of to two people cited with knowledge of the discussion, Millennia’s public offering is set for later this year or early 2012, at a valuation of $700-$1 billion if not more. The timing of the IPO has nothing surprising to it, Bloomberg reports:

“Millennial accounted for 6.8 percent of mobile-ad revenue last year, up from 5.4 percent in 2009, according to research firm IDC. The company has carved out a niche by serving ads to different manufacturers’ phones and offering an alternative to the larger ad networks.”

Millennial Media recently passed a milestone in context to Android and IOS, and reported that the former has accounted for 53 percent of ad impressions on the network, compared to IOS’s 28 percent. This news came roughly around the time the ad network made another push towards an IPO, and appointed James Tholen to the company’s Board of Directors and Chairman of Millennial Media’s Audit Committee. Tholen currently serves as CFO at BroadSoft, which he helped lead into an IPO last year.

As it inches its way towards an initial public offering, Millennial Media doubled its staff not too long ago. The company is geared for growth, but it’s certainly not the only one. Facebook is also heading towards an IPO, and it may pass that milestone much earlier than we thought. Some analysts believe that the $100 billion social network may have its IPO this year, rather than in 2012 as CEO Mark Zuckerberg promises. LinkedIn, the business-oriented social network, launched its IPO just a few days ago, and is already beating expectations.