This thread is a typical example of why nobody gets rich doing mystery shopping. Why use your energy referring someone for $10 or even less?
Sure recommend your cousin cos she lives 100 miles from where you usually shop. Easy $10 right? But wait a few months then she might refer a bunch of people in the area where you shop. Suddenly you are whining on Internet boards about: all the best shops being snapped up, your favorite MS firm deactivating you and ever lowering fees due to a glut of shoppers.
People in most occupations strive to protect the interests of fellow professionals in their fields. Mystery Shoppers sell out fellow 'independent contractors' and ultimately themselves for the price of a cup of coffee. Truly fascinating!