We work with companies to implement a series of achievements (kind of like a "quest line") that the user can complete over a period of time, which walks them through all the best features of the site, hopefully increasing its overall attractiveness to the user. Completing the various achievements earns them SurfScore, which can be combined with any SurfScore earned elsewhere in the SurfScore MarketPlace, which is maintained by us. The idea is to bring them in with the points, and then let the best parts of your website keep them coming back later.
We've definitely got a chicken-and-egg problem, which is why we've started with integrated quest lines on familiar websites Facebook, YouTube, and Twitter, as well as featuring daily achievements to keep people coming back. We're hoping to get some feedback on the UI, as well as how this sounds as an alternative to traditional ads.
http://www.surfscore.com