Just another comment. If Delta's purpose was just to allow us to earn FF miles quicker, than the double miles (only) promo is valid.
However, the key point of the promo is to assist in Medallion requalification. Since there are 2 ways to qualify (miles or segments), it seems only fair that the 2x bonus should apply towards both.
I still don't see how offering double base segments is any worse than double base miles.
Jeff