This is another example where the viral nature of Twitter appears to be driving demand up higher than anyone may have expected. There were more than 2,000 tweets within the first 48 hours that announced what customers were going to order at McDonald's with the #AmexMcDonalds hash tag.
One of the reasons that the marketing campaign appears to be so successful is because it is both simple, and actually worthwhile. For example, those paying with their Amex cards at Whole Foods (a natural foods market) get $20 off purchases of $75 or more. That is a great offer for simply tweeting something so basic. The fact that sending a tweet takes seconds, and the fact that monetary gain is so great, certainly helps. The McDonald's is also good; sending out a #AmexMcDonalds hash tag gets the $5 off their next purchase at the fast food giant.
Within days, the synced cards of customers receive the appropriate credit. This is after they confirm their enrollment in the deal with @AmexSync. Other launch partners include Ticketmaster, Seamless.com, Sports Authority, FedEx Office, Cheesecake Factory, Gulf Oil, Century 21 department stores, Zappos.com, FTD, and Best Buy. Just another clear example that if you provide the customers with something simple and rewarding, they are going to reward you with their business.