A lot of the points this presentation lists (make it a game! reward with points and levels! make users curious by hinting at hidden information!) are techniques that have been used extensively by the most successful Facebook applications. I look at Facebook apps as a bit of a primordial soup of Darwinian evolution, because of the short development cycles and easy access to a potential audience... and the fact that the presentation sums up many of the techniques I noticed succeeding on Facebook is what makes me take it seriously.

Highly recommended for anyone working on consumer apps. Even if you know a lot of the concepts already, it brings them together nicely.