I too am bombarded by emails from Mystery Shopper to sign up for their paid program. Every now and then I get one that says "Okay, we give up...we are desperate for new shoppers. We will give you for free a one month membership". Of course after that you will need to pay their monthly fee. And they do appear to have many, many jobs on their boards. I have been offered a few jobs that seem to come directly from the company requiring the shopper. No fee required. I haven't yet started so, am not sure. Once I'm up and running I may go back and try one of these shops and see what happens. Will let everyone know.
I've also received the email regarding a large cheque coming my way to be deposted and then forwarded on. I hope everyone knows they must never do this...they will be out the money. It is a scam.