The third result to https://google.com/search?q=travel+show+exposing+cons is https://en.wikipedia.org/wiki/Scam_City 

> Scam City is a television show which started airing on Travel + Escape in June 2012, and has subsequently aired on the National Geographic Channel and in Australia on the subscription channel Nat Geo People. Host Conor Woodman travels to some of the world's most popular cities in an effort to expose the darker side of tourism.

Edit: of course, this is television. They will focus on the criminals in a city where millions of honest, everyday people live. While being aware of some scams is not a bad idea, having bad expectations based on this show is not warranted. Not to mention at least the Prague episode was staged with hired actors. Check articles like [Common scams](https://en.wikivoyage.org/wiki/Common_scams) or [40 tourist scams to avoid](http://www.telegraph.co.uk/travel/travelnews/10980488/40-tourist-scams-to-avoid.html).