Millennial Media, the largest independent mobile ad network, has just released their December report. Over the past several months Android has been inching closer and closer to overtaking iPhone in the delivery of mobile ads, or ad impressions. In the December report Android served up 46% of the mobile ad networks ads while iPhone came in at 32%
In the November report the two operating systems were neck and neck at 38%. Rim/Blackberry came in at 16% while Windows came in at 1% (way to go)
As far as devices go, the iPhone was number one followed by Samsung. Samsung had two entries, all of their Android phones and their one Windows phone was the only Windows phone to make it in this month.