The decision to prevent sideloading dates back to the release of the App Store. Upon release of the App Store, Apple charged a 30% royalty on every app sold. De

The decision to prevent sideloading dates back to the release of the App Store. Upon release of the App Store, Apple charged a 30% royalty on every app sold. Developers were outraged by these fees, and fought against them. If Apple allowed side loading, then developers would sell their apps on their own websites and then tell users to sideload the apps. Apple had to prevent side loading to ensure success of their App Store. At the time, people with a developer account could always sideload apps, however they were much more difficult to obtain back then (had to send in verification). Security was not the primary consideration. iOS was a rushed project and it took them many revisions to implement security features. In iOS 1.0, all apps ran as root. iOS didn't have ASLR until 4.3. This was fine since mobile malware barely existed back then. I would argue Apple's sideloading motivations are primarily monetary based and for "protecting the user experience" (typical Apple PR talk). Why though, does android allow sideloading? I'd say it is because Android was ~2 years behind iOS and they needed to catch up. Therefore they made it very easy to build apps for their platform and let any developer install/test apps without an Android Market account. Also Android chose to be open source and there is little stopping someone from building their own version of Android without sideloading restrictions.