Lucky says that American Express Platinum cardholders get 300 Membership Rewards points for using a Delta lounge. You get lounge access when flying Delta, and they’re incentivizing you to use the benefit. When they swipe your Amex they give you a certificate to redeem for the points. In Atlanta, Detroit, Minneapolis, and JFK you could presumably even lounge hop for more miles. And since you get Amex points, you could even be earning Continental or Aeroplan miles for visiting a Delta lounge!
The Points Guy invited MrPickles to guest blog, and we get a detailed discussion on using Big Crumbs to earn cash back buying gift cards. You earn the miles for the purchase, and even after paying any fees and shipping you make money on the deal. (Promo code EMMOTCM waives fees on purchases of Amex gift cards through June 30.) This is useful for meeting the minimum spend requirements to earn bonuses from credit card signups.