I don't know... I've done shops for them and they are super tedious and they require a TON of detail. The shops can take anywhere from 15 minutes to over an hour. Plus usually I see they make you shop a specific target and then it can be hard to work the shop into your day. Also many times the targets just happen to dissappear when you go in to see them and you're stuck making excuses of why you can't let someone else show you around. I knew someone who was identified immediately because she said that she would wait around 10 minutes for the target. Apparently most potential customers won't wait.
Anyway, last time I shopped for them, I spent at least 15 min. of my day trying to reach the target by phone. Then the actual shop took about 45 minutes. I spent a good hour at home putting in the report. 2 hours of work for $40 seems great until you actually do one of these shops. But whatever, to each his own. Bank teller shops are my cup of tea.