Nintendo needs to connect your Virtual games to your My Nintendo account only and not your Wii or your DS. Then the games you buy can be downloaded onto a single Wii and DSi, or if Nintendo wants to play hardball at least your choice of either Wii or DSi.
But, right now, if you buy Wii Virtual COnsole games and you sell your Wii then you lose your entire investment. I know I already made that mistake, and I even disconnected my Club Nintendo account from my Wii and wiped the memory. All my games are gone...if I had understood that was going to happen I wouldn't have done that so at least the person I sold my Wii to could play the games.
Connecting it to a device instead of an account is a horrible idea Nintendo, and it makes me less likely to get into the virtual games arena again. If Nintendo allows you to play VC games on the DSi, I will be upset, because I will have purchased over $100 in games I can't access and play. And I won't even be able to transfer them over to Wii 2 when it comes out.
Bad form Nintendo, Bad Form. I blame myself for the mistake, but you Nintendo should have built a better mouse trap.