• by Laurie Sullivan  @lauriesullivan, January 6, 2011

Mobile ad network AdMob receives more than 2 billion ad requests per day -- more than quadrupling during the past 12 months, according to Google. The stats released Thursday suggest that more than 100 million unique Android and iOS devices requested an ad each month, nearly doubling during the past six.

Growth continues to accelerate in the U.S., but nine countries generated more than a billion monthly ad requests in December 2010, up from just one country a year ago. The strongest region in monthly ad requests during the past year came from Asia with 564%; Western Europe, 471%; and Oceania, 363%.

While Google acquired AdMob last year, taking more than half of the U.S. market share, when it comes to the number of smartphones in the hands of U.S. consumers, Research In Motion (RIM) owns the market. The November 2010 comScore MobiLens report, also released Thursday, found that 61.5 million people in the U.S. owned smartphones during the three months ending November 2010 -- up 10% sequentially.

Research In Motion (RIM) led with 33.5% market share of smartphones. After several months of strong growth, Google Android captured the #2 ranking among smartphone platforms in November with 26.0% of U.S. smartphone subscribers. Apple took 25%, followed by Microsoft with 9%, and Palm with 3.9%.

The data identifies key trends in the U.S. mobile phone industry, ranking mobile original equipment manufacturers (OEMs) and U.S. smartphone operating systems (OSs) according to share of mobile subscribers ages 13 and older.

AdMob isn't the only ad network to capitalize on the growing ad trend in mobile. Millennial Media Wednesday announced raising $27.5 million in venture capital, with Bessemer Venture Partners, Columbia Capital, Charles River Ventures (CRV), and New Enterprise Associates (NEA) participating in the funding. This investment brings the company's funding to more than $65 million. The company plans to use the funds to accelerate global growth plans.

A recent published IDC report suggests that Millennial Media holds 15.4% of the mobile display ad market, behind Google at 19% and Apple at 18.8%.