Well it only asks for a name if they other person hasn't added you already... I guess so they can put some name down since names are private information that can only be seen when both friends have added each other
3DS better be getting an account system update before the Wii U gets released, like preparation for the new system... though they'll probably do it like last minute
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http://img.imgcake.com/GuessMyUserName/tsukemagifda.gif