This is really excellent news, and truly makes World of Goo the poster boy for WiiWare. That's an unbelievable return on investment that these two guys completely deserved.
As to the numbers, I'm pretty sure they meant 55-60% of the sales of World of Goo came from WiiWare, not revenue or net profit. The quote from the article is: "He revealed, via a chart, that 25 percent of all World Of Goo sales in 2008 came from 2D Boy's website, and Steam was a smaller slice. " And IGN also says the same thing in their article: http://wii.ign.com/articles/965/965440p1.html
Either way, this definitely supports the fact that if you put effort into making your game, sales will follow. Hopefully more independent developers will think about putting their new game on WiiWare.
# of games above 75 on Metacritic (including downloadable):
360: 241 DS: 144
PS3: 152 PSP: 126
Wii: 85
