I'm still new to mystery shopping, but as far as I understand the company, they are a company that you pay to search for jobs. They do not pay you directly, nor are they a mystery shopping company themselves. They are similar to Jobslinger (if you are aware of that site), only they charge a fee to view and apply to certain jobs.
You can get around paying them by signing up with many companies directly. I found shadow shoppers initially when I started my hunt, but didn't like the idea of paying a fee. So after googling more, I found this forum and signed up with the majority of the companies that are positively discussed here. I do not pay shadow shopper to gather the info for me, I do the research myself.
Mostly, I believe the fee is to cover the convenience. But I'm sure someone more experienced can answer your question better than I can.
I think they just scan mystery shops, and companies you maybe interested in. From what I get from the site they just filter shops for you. Instead of you searching there tons of shops they do it for you, and email shops your most interested in. I could be wrong I'm new too.
When I first started I signed up for their nearly useless free service. I received way too many emails about doing surveys and about signing up for the $4.95 service. Totally annoying. It took many attempts to extricate myself from their mailing list - unsubscribe did not work. I finally marked their emails as spam, and after about a week or so the email flood ended. Much better for me to use a combination of jobslinger and my own research.
That's what I figured after I looked the site over a little closer. Took a couple of the tests and when they said that you can make $40,000 a year doing mystery shops I decided to call Bull S*** on it. Next time I do my surfing for more work, will be after the cold medicine has gotten out of my system.
Not worth any money in my opinion, they aren't really an MSC, just a bulletin board. I was on their site a year ago and earned enough credits filling out surveys where I got a free month of their gold membership. There was nothing in there I hadn't seen before. When you go to their "job board," the shops listed there just tell you how to contact the MSC who actually has the shop, that's it. I wouldn't advise paying anything for Shadow Shopper, just go to the MSC websites and register as a shopper on your own.