Millennial Media, the nation's largest independent mobile advertising network, filed for an IPO in January, hoping to raise up to $75 million. Earlier this month, social networking giant Facebook filed for a $5 billion IPO, putting the company ahead of Zynga, which raised $1 billion in its IPO last year, the largest offering by a U.S. tech firm since Google (NASDAQ:GOOG) generated $1.9 billion in 2004. While it's difficult to say for sure which other wireless companies are planning to file an initial public offering--venture capitalists aren't telling, and neither are the companies--FierceDeveloper identifies the companies most likely to float IPOs in 2012. Special Report
