Mobile ad network Millennial Media just filed  for an IPO of up to $75 million.
The offering comes after several of Millennial's competitors have been bought up by larger players—the biggest deals being Google's acquisition of Admob and Apple's acquisition of Quattro (which became the basis of the company's iAd program). Now, Millennial describes itself as "the leading independent mobile advertising platform company," saying its network reaches 200 million unique users, with 40 billion ads processed in December.
A recent report by IDC  (cited in the filing) says that when it comes to mobile display advertising in the United States, Millennial has 17 percent of the market, making it second only to Admob. And unlike Admob or iAd, Millennial isn't affiliated with a specific operating system or device.
Millennial's revenue has been growing, from $6 million in 2008 to $16 million in 2009 and $48 million in 2010. That growth continued last year, with a reported $69 million during the first nine months. However, the company has lost money every year (it lost $7 million 2010), and it expects operating expenses to "increase significantly in the foreseeable future."
In addition to the company's financial losses, the filing points to other risks, including whether Millennial has the resources to take on larger competitors, and whether the data collection practices that its business "depends on" will face resistance from either government regulation or industry standards.
Millennial also points to some strengths that supposedly differentiate it from rivals, including its "large and growing" collection of anonymized user data, its audience targeting, and its technology platform, which it says is "architected to deliver mobile advertising at scale, rather than applying traditional online advertising technology or focusing on a particular mobile operating system."
The company may not face a particularly welcoming public market. After a warm welcome for LinkedIn in May, investors seemed to lose their enthusiasm for tech startups  as the year wore on. Groupon and Zynga, for example, are now trading below their initial price, and only Facebook is expected to be a bright spot  in 2012.