Here's a video of Yelp's CEO Jeremy Stoppelman and Director of Consumer Products Eric Singley explaining how mobile location technology — that is, your smart phone knowing where you are — is useful to their business.
One such bonus is that users can check in at locations, like on Foursquare. The benefit to that? "I as a reader of that person's review have sort of an extra stamp of credibility on that information. I know that person has actually been to that business." See, who needs complicated computer programs to detect fake reviews when you can just see if a reviewer checked in on Yelp?
Video: Yelp on Leveraging Mobile Location Technology
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