http://kotaku.com/claim-your-nintend...-id-1792561477
You can now claim your unique Nintendo Account User ID for the Switch. Users who already have Nintendo Accounts may not yet have Nintendo Account User IDs, which explains to rush to claim one.

So far, there are a few Nintendo account types you can make:

  • A Nintendo Account: The e-mail and password combination through which you access the great majority of Nintendo services.
  • Nickname: However you want to be referred to by Nintendo services, i.e. your first name.
  • Nintendo Network ID: How Nintendo users interfaced with the Wii U’s and 3DS’s eShop and Miiverse.

Now users are being prompted to create Nintendo Account User IDs. Switch buyers are already claiming theirs by logging into their Nintendo Account. Why? We don’t know. Sure seems like a confusing number of accounts. Perhaps they’ll replace NNIDs.

Hey, better safe than sorry, it seems. What if 420BlazeIt snatches that User ID out from under you?
(via Wario64)
I got "InsaneJ" so I'm good, at least until Nintendo decides to add another account system