Double miles until the end of the year on Delta

In what could be one of the largest frequent flyer promotions of the year, Delta has decided to offer double miles on all flights, in all classes, flown between now and December 31st.  The Delta promotion is available to Amex Delta SkyMiles card holders only however.  While many Delta frequent flyers already have the card, it may be a significant enough promotion to convert those that don't.  Either way, enjoy it while it lasts.