Heyzap [YC09] adds achievements to its mobile gaming platform
venturebeat.com
venturebeat.com
So basically, this created a feedback loop where Android had many more users than the iPhone app. Indeed, the iPhone app didn't get alot of attention until recently, but in the last couple of months it (and the iOS SDKs) reached feature/design parity with the Android app. We also recently added a sales team member whose focus is on iOS developers, so if things go well we'll add many more users to iOS.