"Shared Photo Streams requires iOS 6 on iPhone 4 or later or iPad 2 or later, or a Mac computer with OS X Mountain Lion. An up-to-date browser is required for accessing shared photo streams on the web.
VIP list and VIP and Flagged smart mailboxes will be available on iPhone 4 or later and iPad 2 or later."
This completely juxtaposes with what happened to iPhone 3G in iOS 4 beta. The iPhone first supported multitasking and a home screen wallpaper. Then since it was too slow both features were removed. However the iPhone 3GS and iPod touch 4 got more features because they were too fast.