This is the first time I have heard Steam described as a positive example in curation in a long time. They're terrible at it. And as others have pointed out here, they have a MUCH simpler curation problem than Apple or Google have to face. I think even Windows Phone or Blackberry have a bigger app curation problem than Steam has an app curation problem. And Valve's response to this is that they want to move to a model of even LESS curation, because running the disaster pit that's Steam Greenlight is too uncomfortable for them.