AmEx is offering credit to customers who tweet their promotions.

It’s one thing for a brand to have millions of followers on Twitter; it’s another to have that army doing some work for you. American Express recently started offering a credit to customers who tweet an Amex-related promotion (e.g., #AmexWholeFoods, to receive $25 off a $75 purchase at Whole Foods). U.K.-based Park Resorts, similarly, is offering savings and credits to brand followers who share promotional links.

“It’s simple and frictionless,” as Ed Gilligan of American Express told The New York Times. The ease of getting consumers to send a brand’s message certainly saves on media costs, and the message is more likely to be noted (Nielsen reports that 92% of consumers around the world trust recommendations from friends and word-of-mouth more than any other form of messaging). “Micro-affiliates,” as these consumer participants are sometimes termed, is an idea that fits well in a post-Groupon world, where deal-loving consumers respond to offers to save money they may not have spent otherwise.