I think that being a rating system is not facebook's primary goal (facesmash is not that relevant as the primary purpose has changed long ago).
Repu will be a dedicated reputation system.
FaceMash was a dedicated reputation system. The real success was when it stepped beyond being a dedicated rating system and turned into the social media platform Facebook. But after Facebook stock went public the stock price dropped because there wasn't a lot of money coming in. That changed massively when they went mobile and added mobile ads.
If Repu keeps focusing on being a dedicated reputation system I wonder where a) the user adoption comes from and b) where the money comes from.