Today I exchanged friend codes (locally) with a friend who hadn't updated his 3DS at all (still had original settings, no eShop etc).
I looked on his system menu afterwards and he had SpotPass TV, Pokemon BW app and SwapNote all installed!?
I let him play my copy of Mario 3D Land on his system, maybe that was it?
Otherwise I guess I virally gave it to him somehow, I have no idea.
Pretty cool though.