Yesterday Google launched Hotpot, a local recommendations engine that leverages Web history, your ratings/reviews and those of your network to offer personalized local business suggestions as part of search results. I wrote about it briefly on Screenwerk.
The success of Hotpot in the aggregate and for any individual in particular is based on participation; you actually have to connect with friends and rate places to see the benefits. After about 10 minutes of doing that online I started to feel fatigue (I've also got jetlag). But mobile is where this really has the potential to take off in my opinion. Ratings generated via mobile devices will also show up online as well.
Right now "rate and review" is a bit buried at the bottom of business profile pages in Google Places/Maps for mobile. But over time it will likely become more prominent, prompting people to quickly rate local business and attractions on the spot. Over time I could well imagine the majority of reviews from the system coming from mobile devices.