Android snatched the ad impressions top spot from Apple over the course of 2011, according to The Year in Review Mobile Mix report from Millennial Media. With Android impressions growing 504 per cent year-over-year,  the OS held a 47 per cent share of impressions on Millennial's platform over the course of the year, up from 30 per cent in 2010. iOS, meanwhile, fell to 33 per cent, after being the number one OS in 2010, with 41 per cent.

It was better news for Apple on the device front – as in 2010, it held the top spot for both manufacturer and handset, with the iPhone.

The report also reveals that wi-fi is on the up – impressions via a wi-fi network grew 21 per cent year-over-year, making up a total 27 per cent – while feature phones are on the out, with the most popular feature phone coming at number 16 on the overall list of handsets – compared to fourth place in 2010.