they just crawl yelp like any other site, yelp happens to use semantic markup (microformats) on its data. Google does show special search snippets, and _used_

they just crawl yelp like any other site, yelp happens to use semantic markup (microformats) on its data. Google does show special search snippets, and _used_ to show yelp review snippets on place pages, thanks to the microformats markup.