Interesting, from the official rules:
NO PURCHASE NECESSARY. A PURCHASE WILL NOT INCREASE YOUR CHANCES OF WINNING. NON-PURCHASE ENTRIES AND PURCHASE ENTRIES HAVE AN EQUAL CHANCE OF WINNING. VOID WHERE PROHIBITED OR RESTRICTED BY LAW. To enter the Alaska Airlines Million Mile Giveaway Sweepstakes (the "Sweepstakes"), each entrant must be a legal resident of the U.S., residing in the Safeway Inc. Seattle Division (Alaska, Idaho, Montana, Oregon and Washington), and must also be eighteen (18) years of age or older as of September 24, 2008
But from the enrollment page:
*Alaska Airlines Mileage Plan Miles can only be earned at Safeway locations in Alaska, Washington, Idaho and Montana. Online shopping at Safeway.com only available in Washington State service areas.
Unfortunately, the enrollment page is "more" right, as Safeway's Portland Division covers Oregon (Except Hermiston) and Southwest Washington. Those of us in the Portland division are stuck with United miles.