i know the reason people don't think this could be used as a 'normal' memory card is cause of the stupid file count limit inherent in the GCN. Theoretically though, wouldn't it be possible to put software on the sd, format it if you will, so that it could act as multiple memory cards. So that you would then have to pick which virtual memory card on the sd card you wanted for a particular game?
Also, do you think nintendo is going to package an sd with the adaptor? seldomly does one find a store that would sell both a nintendo accessory and sd cards unless its like a comp usa.