At the bottom of the page he mentions Yelp, and looking at their robots.txt they have this weird stuff for each of the allowed bots:

  Disallow: /biz/outlook-autumn-market-fundamental-catwalk-flimsy-roost-legibility-individualism-grocer-predestination-0

And over and over ten times. Trying to see if the bots ignore robots.txt I guess?