Wii's does not have an online platform yet, it has online functionalities.
Nintendo does not want to emulate what PC, PS3 and Xbox360 have. This is not because of arrogance nor cheap savings, but because Nintendo prefers to gather people around a single console to play multiplayer and have fun (NSMB Wii). Their online infrastructure is aimed to add services that makes entertainment (in general) more enjoyable and sometimes ease the customer's lifestyle (the services in Japan for example).
Nintendo's online platform is aimed to a broader audience than just gamers from the very begining (hence the difference from Live and PSN), maybe broader than even Facebook. This makes me believe that the online infrastructure is way more robust. But to have all they want to add costs a lot of money so I think they are building it in stages.







