I have an amex Delta Reserve card that allows me to accrue up to 15k MQMs with $30k spending twice in one year. I have to request that these MQMs be added to my Skymiles balance.
On October 8th of this year Delta spontaneously deposited 15k MQMs to my account with no warning or explanation. I doubted that these were a spending threshold (because I hadn't made the 2nd threshold). Coincidentally, this was the date of the Northwest/Delta milage program. Last week, they spontaneously removed the 15k MQMs.
As an aside, this also happened to my significant other. The boost pushed him to platinum and they have yet to reverse that error (much to his delight).

Does anyone know what was going on?