Congrats to these guys! These guys were stealth from funding to acquisition. Seems like this will be the Google equivalent of Yelp.
I see them less as an equivalent to yelp and more as a way of providing instant feedback to business owners. It seems more a feedback system than a review site. I haven't had the chance to try it out though so this is based purely on what I've read about them.
For a pedestrian example, think of the times you've called your cellphone or power company and the recording on the phone tells you to have the helper send you to a satisfaction survey. Now transpose that to proximity services: you leave a restaurant and your phone pops up, "Thanks for visiting! Care to tell us how we did?" ...which is then popped-up to the manager. Googlers are smarter than me, so I'm sure they have more nuanced and lubricative plans, but you get the idea.
Yelp deals with what you're planning or where you've been, bracketing your experience, and the coupon services act as nudges against your retail future. 'Long as you keep checking your phone, that is. The pot of gold I feel is to reflect where the user will actually go (determination). This is where recommendation engines become useful: to (try to) tell the user where they're going to go. "Rhizome, there's a Taco Bell on the next block. I KNOW YOU LOVE TACO BELL"
The user's time and attention is getting pinched at all times for these services to pull information about where the user is in the retail thought process, and maybe Yelp will have their reactionary review model knocked from under them when recording the reaction takes much less effort on the user's part. Then again, maybe this is all cynical and evil on my part. I don't know. ;)