Right now, for example, you can buy a $25 Amex gift card for $15 by Tweeting #BuyAmexGiftCard25. Then you check your Twitter mentions until you receive one from @AmexSync containing a confirmation hashtag.
Tweet this hashtag within 15 minutes to complete the purchase. They’ll now ship the item to your billing address free.
It’s just my opinion, but Amex needs to look up the definition of “seamless”.