@Quitchan Nintendo stated:
unauthorized versions of several games, and
Nintendo 3DS systems that stored the unauthorized game code have been banned from Nintendo’s online network effective immediately.
My old 3DS has FBI and I have played Mario Kart 7 online and have not been banned yet. I'll update after a day and see what happens. But I'm lead to believe that they added something in the new firmware update that can detect, and phone home your installed titles and cross-reference it with your e-shop account and if there's any mis-match you may get banned.
Honestly though, if you wanted to play online, you should have 2 3DS's anyway.
1 that's hacked for pirating and rom hacks/homebrew/etc.
1 that's legit, never hacked for playing online.
Microsoft does this, Sony does this, Steam and Origin do this. I'm shocked that everyone is so surprised that Nintendo is now doing this.