Would have to be an organized campaign - cause and effect, and names on a list. These people, you see, will not buy anything at Macy's or Mervyn's this year. They will donate to the Boy Scouts and Salvation Army instead. It would have to be that organized for big-boxers to notice. Worse yet, you took your trade to the remaining proprietary resellers, avoiding the big box. I, personally, would still be reluctant to boycott Costco. They have quite a good stock.
Do not include Menards, Home Depot and Sam's Club or Wal Mart in your "Big Box" boycott they all have their heart in the right spot.