I actually like that the 3DS uses a friend code for the system account, because it allows two or more people to use the same name. I'm pretty sure that two XBox Live accounts cannot have the same name, though I don't know how PSN works.
There are some Wii games that let you exchange codes with strangers, and even chat with them. Call of Duty: Black Ops, for example, allows you to add the random people you come across, and everyone on your team can hear you if you're using a headset, whether or not they are on your friend list. Monster Hunter Tri also allows you to add randoms and text chat with anyone, though Wii Speak works only with people on your friend list who also have a Wii Speak. It may not be a system feature and Nintendo may not use it in their games, but there is nothing stopping third-parties from allowing these features. It would be nice if Nintendo did make them standard features of the Wii U though, so developers wouldn't have to implement them on a game-by-game basis.