• by Mark Walsh  @markfwal, February 23, 2012

Full-year data released by mobile ad network Millennial Media underscores how dramatically Android expanded in 2011 -- at the expense of Apple’s iOS platform.

Android impressions increased more than 500% on the network, propelling the Google mobile operating system from 33% to 47% share of all impressions. At the same time, iOS impressions dropped from 41% to 30% last year.

BlackBerry-maker Research in Motion held fairly steady during 2011, dropping to 16% from 18% share of impressions.

The Millennial findings roughly parallel the most recent comScore data on overall U.S. market share for the top smartphone platforms. It showed that Android had 47.3%; iOS, 29.6%; and BlackBerry, 16% as of December.

Apple, however, remained easily the top manufacturer on the Millennial network, while the iPhone was the leading handset model. Apple devices accounted for 26% of impressions last year, unchanged from 2010. The big gainer last year was HTC, which nearly doubled its market share to 14% and pushed past RIM to rank as the No. 3 manufacturer behind Apple and Samsung.

The iPhone’s market share over 2011 dropped only slightly to about 15% -- still well ahead of its nearest rival, the BlackBerry Curve, at almost 6%. Both Samsung and HTC had four phones in the top 20 on Millennial’s network, highlighting the dramatic  growth both enjoyed in 2011 on the strength of Android device sales.

Reflecting the spread of smartphones and tablets, the proportion of touchscreen devices used on the network increased from 46% to 57%. The share of smartphones themselves grew from 55% to 68%, with feature phones as a result falling from 31% to 17%. Driven mainly by iPad sales, the share of other connected devices rose to 15% from 14%.

Looking at mobile applications, Millennial found gaming titles were the most popular in 2011, followed by music and entertainment, social networking, communications, and news apps. News as an app category moved up to the No. 5 slot from No. 8 last year.