The second-largest mobile ad network Millennial Media -- the one not acquired by Google or Apple --just filed for its initial public offering.
The company, which sells banner ads on mobile websites and smartphone apps, reported $69.1 million in revenue in the first nine months of 2011, up 138% from the prior period, according to a filing with the Securities and Exchange Commission. The company is not yet profitable.
Millennial owned 17% of the $630 million mobile display ads market in the U.S. last year, second only to Google's 24%, according to research firm IDC. Baltimore-based Millennial, which has raised more than $65 million in venture capital, likely benefit from Apple's stumbles. The iPhone maker's ad unit, iAd, lost market share from 2010 amidst gains from both Google and Millennial.
Both Google and Millennial's Apple acquired Millennial's peers in recent years. Google acquired Admob for $750 million following Apple's purchase of Quattro Wireless for as much as $275 million. Google agreed to buy Admob before the Apple deal but the transaction was held up by regulators.