There is a catch. You have to tweet a special hashtag that corresponds to each deal before you can claim it, so you’re doing a little advertising.
For example, to get $5 back on your next $25 purchase at Gulf Oil, you have to send out a tweet that includes this hashtag: #AmexGulfOil.
An automated notification system will detect your tweet if your card is linked to Twitter and send a confirmation tweet back to you. That way you can go ahead and make a charge knowing you’ll get money back later.