AppleInsider reports that according to the latest report from InMobi, the biggest independent mobile advertising network, Apple’s share of available ad impressions in North America rose impressively from 23.2 percent in October 2011 to 35.3 percent in January 2012, marking a rise of 12.1 percent, just at the time that Android’s share fell by 3.2 percent, down to 32.7 percent. This puts Apple back in the top spot, with Google now behind in second place. As AppleInsider notes, this is a definite improvement for Apple from most of 2011, when Android was the top platform tracked by InMobi for the majority of the year. InMobi’s figures also show that RIM’s BlackBerry iOS had another big fall in ad impressions from October to January, down by 8.9 percent to 11.6 percent, putting it in third place.

"The iOS growth we are seeing may be attributed to the tremendous success of iPhone 4S and iPad in the ecosystem," Anne Frisbie, vice president and managing director for InMobi's North American operations told AppleInsider. "Overall, we are excited to see InMobi’s available impressions exceed 55 billion in North America, and look forward to continuing our rapid growth through 2012."

Source: Apple's iOS passes Android, accounts for 35% of mobile ad impressions