I believe roughly that by the time Wii gains 50% market share, 30% of Wii owners(that's 30% of 50%) will own at least one of the other consoles. I think this may drop lower with time though as more games come up. Eventually, 90% of people who own a 360 or a PS3 will own a Wii.

@Grey Acumen

been said before, most people that own a Ps360 don't care about a wii

Owning a Ps360 however, is redundant. Those people are very few and far between. I would assume it is the least popular combination.

PC/insert system here 

Wii60

PSWii

PSWii60

PS360

That'd be my guess, considering everyone has a PC, and the second most redundant combination is a PS3 and a 360.

I had all 3, but never both. I bought my Wii first, actually. 

You vote with your $ so they do care. If the 360 started out with a failure rate of 1% how many more units would have sold how much more money would they have saved. Why do you think all these companies hire huge PR (public relations) firm. So that you will trust them and buy there product. They may not care about you but they sure as hell care about what you think because that translates into what you buy. So yeah them caring about money is a good thing and I didn't even mention there fear of lawsuits.