I stumbled on this Yelp snippet the other day. Normally you would expect to see rich snippets increase the click through rate of your result, but in this case, I doubt it.
What if Yelp would be smart with Rich Snippet optimization and take it one step further. Dynamically implement the schema code based on the review score. This way you could avoid 1 star reviews to show up as rich snippets in the SERP's.
>If AggregateRating =< 3 don't implement AggregateRating markup
>If AggregateRating >3 implement AggregateRating markup
This way, Google would most likely not show a one star review rich snippet for those places which suck...