I really love this idea. This simple act of generosity to make another person (stranger) happy without asking for anything in return.
The first time I've heard of pay it forward, was when someone mentioned this article to me.
I also really like the idea of creating special orders for specific people as Shawn mentions:
"At A Cup of Common Wealth customers can buy a specific drink for a specific person or type of person. Such as “a medium coffee for a a middle school teacher” or “an iced latte for an Alaskan traveler”."