Though it's just one measure of mobile market share, a look at ad network InMobi's projections for the rest of 2011, based on its ad impressions suggests Nokia's jump to Windows Phone couldn't be better timed.

Combined, Nokia's own OS and Symbian serve up 38.6 percent of all ad impressions globally, based on the most recent quarter ending July 2011.

By the end of the year, however, the picture will have changed, with Android coming to prominence just as Nokia rolls out its first handsets running Microsoft's OS.

A tale of two platforms

It's the Finnish firm's platform that officially sits in top spot, but InMobi projects Android – which currently accounts for 16.6 percent of impressions – will have slipped ahead before the year is out, owing to increasing demand for Google's OS.



Interestingly, it's this ascent to the top that, for VP of global research and marketing James Lamberti, explains Google's $12.5 billion purchase of Android OEM Motorola Mobility.

"Given Android's ongoing growth around the globe, it's not surprising to see Google announce its strategic move to acquire Motorola Mobility," offerd Lamberti.

"At the current growth trends, Android is expected to become the top mobile platform in the ad ecosystem by year-end and Google is clearly protecting its mobile platform from competitive threats with the IP assets of Motorola Mobility."

Eye on America

InMobi claims its impressions on its own network are up 22 percent, having served 112.5 billion ads during the last quarter.

North America in particular is expanding at pace, InMoni claims, with the region accounting for 20.9 billion impressions, or 18.6 percent of the global total.

The firm's quarterly report in full can be downloaded from InMobi's website.