GrubHub offered a $12 coupon for each friend I referred who created a new account and placed at least one order. They offered the same coupon to the friend who signed up, so I was able to get 4 friends to sign up. They all got their coupons. I never got any. I contacted GrubHub about the issue, and they told me not to expect any coupon codes.
Thanks for lying, GrubHub! I had been recommending you to my friends. But I'll be sure to update them all on your stellar service. And by service I mean fraud.