On Facebook, a restaurant that I "liked" posted a photo of one of their servers standing alongside the owner of the company, praising him for a perfect "shop". He got a score of 100 from a mystery shopper for excellent service.
I thought it was so great that they featured him on their page and made a big deal out him doing well. He was beaming in the photograph, and so was the owner.
I think some people have the misconception that mystery shoppers are out to "get" employees, but I know that I always feel much better doing reports where I can sing an employee's praises, rather than a negative report where there were a lot of problems to point out.