In the Netherlands you can even buy simcards in supermarkets, almost every supermarket is a virtual provider itself. If you go to a telecomshop they'll install it for you. Your describing something that's completely foreign to everyone over here.
This would potentially allow you to change providers (O2->3, Vodafone->giffgaff) without needing to go to any physical shops. Just get a new contract online, apply it to your sim card. You get to also keep your number without having to fiddle with PAC codes and activation timeframes. I guess.
