App Store (iOS)
While Apple wants the App Store to be available worldwide, their market is restricted to country borders. Different countries have slightly different app stores. Some apps may only be available on the app stores of a few countries, while others can be available in many countries. Trying to use an app store of one country while in another may be a problem: Apple warns that "one of the risks of creating a German account while you are in Greece is, our system may able to detect it and it may put restrictions on your account (German) that will prevent you from using the iTunes Store".