My wii drive started getting disk read errors so I downloaded a lot of games thatI already own and got a HDD for my wii, It is now my prefered way to play games as I never have to swap the disk around. But once you got it all on your wii it is very tempting to just download games you dont own to try them out.
As someone who copied large number of games in the amiga era I know that I never enjoy them as much as the games I purchase so its definatly worth still buying them.
The thing that annoys me even more than this is the preowned game market, I feel a lot more sales are lost due to this than lost with piracy, and it effects all consoles not just wii.