More and more, people are moving away from their PCs and instead using their smartphones. Consider that according to research from Kleiner Perkins Caufield & Byers, mobile traffic on Facebook has gone from 1% of total traffic in 2008 to 33% in 2011.

So far, there have been few opportunities for IPO investors to tap into this mega-trend. This might change in 2012. This week, Millennial Media filed the necessary papers with the Securities and Exchange Commission for a $75 million public offering. The lead underwriters include Morgan Stanley (NYSE:MS), Goldman Sachs (NYSE:GS) and Barclays (NYSE:BCS).

Based on the surveys from IDC, Millennial Media is the No. 2 player in the mobile display advertising segment in the U.S., with a market share of 17%. The top operator is Google (NASDAQ:GOOG), which has 23.8%, and Apple (NASDAQ:AAPL) is No. 3 with 15.1%.

Millennial Media’s technology platform MYDAS essentially makes it easier for advertisers to reach as many as 200 million unique mobile users, while at the same time allowing app developers to generate revenues.

Mobile advertising certainly has some key advantages. People usually keep their device with them at all times. This makes it possible to advertise anytime, anywhere. It also makes it possible to target audiences based on behavior and location.

So far, Millennial Media’s technology is embedded in more than 28,000 apps and processes over 1 billion ad requests per day. Customers include Pandora (NYSE:P), Zynga (NASDAQ:ZNGA) and CBS (NYSE:CBS).

And Millennial Media has been growing at a fast clip. Revenues for the first nine months of 2011 came to $69.1 million, up from $47.8 million in the year-ago period. However, the company did register $417,000 in losses last year.

But going forward, the growth ramp is likely to continue. Gartner Inc. predicts global advertising revenue will go from $1.8 billion in 2011 to a whopping $13.5 billion by 2015, which translates into a 65% compounded annual growth rate. So even with the fierce competition in the space, Millennial Media should have enough opportunity to remain a top contender.

Tom Taulli runs the InvestorPlace blog IPO Playbook, a site dedicated to the hottest news and rumors about initial public offerings. He also is the author of “All About Short Selling” and “All About Commodities.” Follow him on Twitter at @ttaulli. As of this writing, he did not own a position in any of the aforementioned securities.