One of the most talked about features of the latest Apple operating system version, iOS 9, is how it now allows its users to enable ad blocking apps. The big question is, will ad blocking become big for mobile or not? Pointers seem to be heading towards a yes. As it turns out, ad blocking apps reached the top spots on the App Store within a day of the iOS 9 release. Crystal, Purify, these are the seemingly innocent names posing as a threat to mobile ad revenues.