Friend of mine did it once. Company did not like how she wrote her report (she had to print out something like 15 pages of a report). On top of that she was thought the manager of the Denny's she was shopping was going to get violent with her. This was a shop where she had to note down (without anyone knowing what she was doing) every detail of what was said (specialty drinks and specialty foods offered) and not said. Plus she had to reveal to the restaurant manager that she was a mystery shopper at the end of the shop to get a form signed. The food was so bad that they could not eat it so they ended up paying for a really bad meal (her hubby's) but for the "other" meal they ended up buying because the first meal was unable to be eaten. I know that incident occured over 5 years ago and they both will not enter that particular establishment. I'm just glad her husband was along. Based on what she said, I think the manager (female) was going to attack her until her husband walked back into the place to see what was taking her so long to leave. She has never looked at mystery shopper jobs again. Also she said they all seemed to be in larger cities... like Atlanta!