If you have Platinum or Gold with SPG or Silver through Diamond with Delta, then you can register to receive points/miles with one program when you participate in the other. For example:
SPG elite members will earn 1 Starpoint for every dollar spent on eligible Delta flights while still earning your Delta miles. You will also get the Delta benefits of priority checking and free checked baggage.
Delta elites will earn 1 mile for every dollar spent on eligible room rates for SPG properties plus other benefits while still earning Starpoints. You will also get the SPG benefits of late checkout, complimentary internet and upgrades if available
These benefits start March 1, 2013 so if you have or going to have elite status with either or, then make sure to sign up to get your extra rewards.
Some T&Cs include only flights operated by Delta or Delta connection will be eligible. Points/Miles will post within 4-6 weeks after stay/fight.