Thanks Again (thanksagain.com) has an ongoing promotion with Alaska Airlines Mileage Plan that is good until the end of the month (3/31/2016).

The promotion is:

• You get 250 miles for signing up and making a purchase at any one of Thanks Again’s 100+ airports across the US (For a full list of airports and merchants, use their locations tool).
• If you cumulatively spend $250 across the Thanks Again Network through 3/31/2016, you get an extra 500 miles bonus.

Also, as a member of Thanks Again you earn 1 mile per dollar spent with every qualifying airport purchase. The maximum Mileage Plan miles you can get from this promotion is 1,000.

See full details here.

This was not mentioned on the promotion page, but I just signed up and already got 100 miles without making any purchase:

So what do you have to do? You will have to set up a profile on thanksagain.com and register a credit / debit card on their system so they can track your purchases.

Should you take advantage of this promotion? Assuming you won’t be making $250+ in purchases, this promotion is basically worthless – 50 cents to be exact( as valued by The Points Guy here). However if you plan on traveling / be at an airport before the end of this month, and you want to keep your Mileage Plan account active (all you have to do use earn / redeem at least 1 mile to extend your miles’ expiration date), or you just want to collect whatever miles you can get your hands on, it’s not a bad idea. I found an array of shops are on their list of participating businesses – restaurants, newsstands, clothing stores, even an EA games retail store. So you if you are to buy something at an airport, you shouldn’t have any problems earning the 250 bonus miles. The promotion did not state a minimum spend, so all you want to buy is a pack of gum, you should still be good.