I think they're going to struggle again - they had that promote/remove button which applied to your personal SERPs, and they've had the starring thing for ages, but there's a fundamental problem with actual social search which is that people can only really be arsed to join in if they have a vested interest..... we care, webmasters care and possibly people who are trying to find [car hire] and keep seeing sites which are just whitelabels of the same quote system again and again care, but none of those people are going to click buttons for the actual reasons Google needs to get accurate data.
I wonder what the potential for 'stupid webmaster self destruction' is with this btw? People who try and hit competitors by repeatedly sending crap feedback but leave their browsing history and evidence of their own sites (or people who visit these sites also visit this one) open to pattern watching as Google hand review data.
OK, I'm too paranoid. i'm also still not installing Chrome.