The world's largest retailer, Wal-Mart, can be just as vulnerable to consumers' changing tastes as any old retailer. Its same store sales have declined for two years in a row, according to the Wall Street Journal today. The retailer, which includes Sam's Club warehouses, needs to find some of the higher income shoppers from which Costco and Target benefit.

Sam's Club wants to get more spenders in the door, so it is offering a 10-week membership for $10. If you aren't happy with the membership, you can get your $10 back. The regular price for a membership is $40 per year.

I'm always surprised that many people say that they can't justify the annual fee because they can't recoup the savings. Seriously? I could justify the savings in one or two trips and I don't have kids to feed. I recommend going through every aisle in the store just once, and you'll be surprised at the variety. When I do that at Costco, I always see an item such as bath mats or entry way rugs that I didn't realize Costco sold.

If you're wondering when Costco will offer a similar deal, don't hold your breath. It's never done membership offers except when a new store opens.

The Sam's Club membership deal is for 10 weeks after you sign up, but the offer is only good through June 5. Click here to find Sam's Club locations in Minnesota.