I don't know if you need both, but proof of patronage alone might not be enough to trust a review (See Amazon verified purchases).
That's kind of an ersatz proof of patronage.
It might be possible to craft a request for that API. And even using a legitimate copy of the Yelp app to make requests, a jailbroken iPhone can change its coordinates to whatever you want. An Android doesn't even need that - just set it to developer mode and you're ready to fake check-ins all day.
http://techcrunch.com/2015/07/28/google-search-now-shows-you...
The average HN user might not care for such a system, but I think many people would find it reassuring for better or worse.
Biases baked into the platform are one problem for a review site. But you also just need critical mass.
I've heard about it all N-th hand, so I'd imagine that Yelp's team is very careful about wording it such that it's some sort of legit promotion that they're offering.
I'm actually sure this has happened, since it's essentially impossible to prevent thousands of salespeople from deviating from an approved script when pushing hard for a sale, but surely it can't be commonplace.
Trip Advisor (most relevant for hotels) and Yelp is supremely bad for surfacing the aspects I care about from the depths of things I don't. It's better with restaurants, as most people seem to agree to a much higher degree on the baseline.
IMO that's an overstatement. I find Zagat, Yelp, and Amazon reviews all useful--however imperfect. That said, however unpopular this opinion may be in our crowdsourced world, professional reviews/ratings tend to be more reliable than random ones on the Internet. The problem is that professional reviews don't scale, especially for local businesses. The New York Times restaurant reviews aren't bad but that's NYC and, even in that case, a lot of the reviews are going to be quite old.
So, in an ideal world, there might be armies of professional evaluators of hotels, restaurants, and other businesses--but that's not the world that we live in. (Films are one of the few areas where you can get a pretty good pool of professional and semi-professional reviewers.)
With restaurants, on the other hand, there is a wide range of quality. Even if the average shopping mall restaurant delivers a hot meal in a reasonable timeframe, I'm probably not going to give it 5 stars.
It's only lately and due to the prevailing rumor of Uber's mercilessness that I give 5 stars to meet "don't fire the driver on my account" and less than 5 stars to mean "I demand a refund and the head of the driver."