Web ad network: iOS 4 on half of iPhones
On a more granular level, the initial July 21 release of iOS 4.0 was discovered on 44.4 percent of the iPhones, while the 4.0.1 update released a week ago was installed on 5 percent of the devices. Among phones still running iOS 3, the most recent 3.1.3 version was on 29.9 percent of them, while the previous 3.1.2 release was found on 14 percent of all iPhone traffic on Chitika's network.Some users ran into roadblocks trying to upgrade to iOS 4, including long backup times and error messages, forcing many to find workarounds to install it. iOS 4.0.1 was released largely in line with Apple's response to the iPhone antenna issue, promising that the update would correct how the reception bars display on the phone.Like rival AdMob, Chitika tracks the number of ads that are clicked on by mobile device users across its network. The future of third-party ad networks has generated some controversy with the debut of iOS 4 and Apple's new iAd platform. The company changed the terms in its iPhone agreement to restrict competing ad networks from grabbing certain types of data.So far, Apple has yet to enforce those policies, giving Google-owned AdMob some breathing room, at least for now. Chitika itself said it's unaffected by the restrictions in the first place. The company told CNET that its ad network is strictly Web page-based and that Apple's policies apply to ads served within mobile apps, not ads served on general Internet sites.

