iPhones running iOS 3.1.3 or earlier cannot access the App Store, no comment from Apple yet
If you are still holding on to an older iPhone model – one running iOS version 3.1.3 or earlier, in particular, you may have noticed that something with your smartphone is not quite as it should be. We are talking about the inability to access the App Store directly from the device, which is an issue that has already spawned a long thread on the Apple Support Communities board.
The problem arose right after a software update was pushed out on December 16. Strangely, app updates seem to work fine, according to a number of user reports, yet downloading new ones is possible only after connecting the smartphone to a computer with iTunes.
source: Apple Support Communities via Engadget
Things that are NOT allowed: