Yeah, in this case it should be Yelp's job to filter out fake reviews. Yelp should foot the bill for operations like this or for engineers to write better algorithms.
After all, I could write algorithms that used more and more information to determine criminality.
I'm pretty sure they do credit checks and run my license.
You would have to insure your cars against theft. If you get robbed a lot, your insurance company would raise your premium.
it already works like your hypothetical scenario, so what's your point?
edit: an analogy from your point to what happened would be the government setting up a fake car rental and calling up thieves to agree to rent and steal their cars.