Millennial Media is growing at a very rapid pace, going as far as to outpace Apple in becoming the second largest mobile ad network operator out there, as of last month. It’s been the largest independent ad network for quite some time now, and last night the company has confirmed that they’re changing this indie status.

Millennial IPO

An email press release said that Millennial has filed papers with the SEC to launch an IPO. Morgan Stanley, Goldman Sachs and Barclays Capital are going to be carry out the public offering.

The company’s statement is fairly brief, not revealing any info about how much capital it’s looking to raise or when, but it does confirm a handful of earlier reports that speculated about such a move by Millennial.

“Millennial Media, Inc. announced today that it has filed a registration statement on Form S-1 with the U.S. Securities and Exchange Commission (“SEC”) relating to a proposed initial public offering of shares of its common stock.”

Millennial has been expected to cash out on all of its recent growth by both pundits and the familiar “closes familiar with the matter,” either via an IPO or an acquisition by a competitor. Apple has been believed to be a potential buyer by some, and others have even suggested Microsoft may be interested.

Out of all the predictions and rumors and anonymous sources, a Bloomberg report we’ve picked up back in May proved to be the most accurate so far. Two different sources have said Millennial would file for an IPO sometime in early 2012, a timeframe that sits in rather nicely with the latest news, and that the company would seek to raise a sizable amount of capital. The same sources said that its valuation will balloon to somewhere in the range of $700-$1 billion.