Rolling carts stacked with 1,000 white flip-flops with the blue American Express logo flanked the entry to the opening party for the Delta Air Lines Global Sales Conference at the Walt Disney World Swan and Dolphin in 2011. As the 850 guests arrived, they swapped their shoes for the flip-flops and headed out to the party set up around the Swan’s pool and beach, where the sandals left logo impressions in the sand as guests walked.