Impossible to play online (err 20115)

[tueidj]

Nintendo owns a heap of OUI prefixes: http://www.coffer.com/mac_find/?string=Nintendo
74 * 2^24 = over 1 billion possible MACs.
Nintendo does rely on the wii's MAC address being unique as part of their security model, look at how letterbomb works for example.
The friend code is generated from a bunch of system unique info, as well as a seed value that gets incremented each time the wii is formatted.