Today we’ve learned that Millennial Media, the largest remaining independent mobile ad network, will grow its staff by nearly 50 percent. This will involve the hiring of about 60 new staff members by the end of the year, and comes as the ad network is gradually moving towards an initial public offering.

“Millennial Media is growing toward a planned initial public offering, taking over a second floor of the Can Company’s Signature Building in Canton and adding staff.”

Millennial’s CEO Paul Palmieri said the company has subleased about 14,000 square feet at that location from online hotel-booking company TravelClick.

We’ve had additional Millennial Media developments too this week, when the company released its monthly Mobile Mix report for March 2011. Millennial’s findings reveal Android is still the number one mobile platform in terms of ad impressions, but IOS is leading the charge with the most app revenue. Android as well as iOS, Blackberry and tablets have seen a great deal of month-to-month growth. Millennial Media’s previous report also had some interesting highlights, especially around location-based marketing and rich media – two of the fastest growing areas in the entire online marketing segment.

Indeed, marketers are finding more and more innovative ways to get to users via the mobile devices, and Motricity is looking to join the club. The company just finalized the $100 million acquisition of mobile advertising company Adenyo. The final price tag, which may even exceed the original $100 million stated by Motricity has not been announced.

Going back to the hiring front, Millennial Media is not the only one who have been adding some extra volume to its staff lately. Another example of an accelerating company boosted by a growing industry and market share is Juniper Networks, who has also been doing some hiring lately.