The company reports that iOS 4 leads iOS 3 by just 1%, with 50% of all iPhones running the new operating system.
The report, which comes from a survey of more than 9 million iPhone impressions across Chitika's advertising network, shows that 49% of phones still run on iOS 3, and a tiny fraction - that 1% difference - still run on some archaic version of iOS 2.
Chitika offers a closer look at the numbers to show that only 5% of iPhones are running the latest update of iOS 4, and a third of those still running iOS 3 are not running the latest version of it.
While we expect that some of the iPhones running iOS 3 are doing so because iOS 4 would slow their phone down (as has been reported with the iPhone 3G), we also suspect that a percent of phones have not updated to keep their jailbreak intact. It would be interesting to see what happens to these numbers when a reliable way is found to jailbreak iOS 4 for the iPhone 3GS.