Nintendo Network IDs are tied to your Wii U, can’t be used elsewhere
While Nintendo’s thrown the whole Friend Code concept in the bin and replaced them with the Nintendo Network ID, it appears that the ID will be attached to the console you create it on. That means you won’t be able to go to a friends house and play on their Wii U with your own ID.
There’s also more adverse problems with this as well, especially if your Wii U was to get stolen or break down. All of your purchases and progress you made on the account will be gone. The news comes from Nintendo themselves and their support pages.
[quote]Q. Can I Log Into My Nintendo Network Account on a Different Console?
A: No, you cannot. A Nintendo Network Account can only be used on the console where it was created. In the future, you will be able to use your Nintendo Network Account with future Nintendo consoles and other devices, such as PC’s.[/quote]
However, there is a glimpse of good news here as you can see above Nintendo states that in the future you’ll be able to use other Nintendo consoles, computers and smartphones to access the network. Baby steps it is.