Mono is HUGE thanks to Unity3D.[1]<p>I suspect that C#/Mono has become the de-facto second development language/environment for iOS thanks to Unity3D (an irony that doesn't escape me). It's certainly what all the iOS games programmers I know personally use (and I know a lot).<p>Wikipedia have Unity down as having over 1 million developers developing for iOS, Android, Windows, Blackberry 10, OS X, Linux, web browsers, Flash, PlayStation 3, Xbox 360, Windows Phone 8, and Wii U.[2]<p>Unity themselves claim[3]:<p>* 2M REGISTERED DEVELOPERS<p>* 400K MONTHLY ACTIVE DEVELOPERS<p>* 225M TOTAL WEB PLAYER INSTALLS<p>* 6.6M EDITOR SESSIONS JUN<p>[1]<a href="http://unity3d.com" rel="nofollow">http://unity3d.com</a><p>[2]<a href="http://en.wikipedia.org/wiki/Unity_(game_engine)" rel="nofollow">http://en.wikipedia.org/wiki/Unity_(game_engine)</a><p>[3] <a href="http://unity3d.com/company/public-relations/" rel="nofollow">http://unity3d.com/company/public-relations/</a>