Native monetization is deriving revenue from a platform in a way that is unique and organic to the experience. It’s the reason why Twitter, Facebook, Foursquare, Stumbleupon, Tumblr, and BuzzFeed avoid just slapping banners anywhere they can fit them.
It's taking the core organic activities and extrapolating them to a paid activity that "fits."
A post I did a while back: jonsteinberg.com