Perhaps if you ever fly NW:

You can add valuable WorldPerks miles to your account when you join Marriott Rewards® and stay at any of more than 2,000 Marriott® hotels around the world. As a Marriott Rewards member, you will earn 3 WorldPerks miles for each $1 USD* you spend at any Marriott Hotels, Resorts and Suites; Renaissance Hotels®; Marriott® Conference Centers and Marriott Vacation Clubsm International resorts. You’ll also earn 1 WorldPerks mile per $1 USD spent at all Courtyard® by Marriott,® Fairfield Inn® by Marriott,® Residence Inn® by Marriott,®SpringHill Suites®by Marriott® and TownePlace Suites® by Marriott®. You choose the hotel that best suits your travel purpose, and enjoy the best in business, leisure, luxury, moderately priced or extended-stay hospitality.

To enroll in Marriott Rewards, call 1-800-249-0800 and mention enrollment code NWMA, or visit www.marriottrewards.com and enter NWMA in the enrollment code field. Make sure to complete the stay preferences form, and give your WorldPerks account number for your designated airline.

http://www.nwa.com/freqfly/updat/marriott.shtml