Warehouse club retailer Costco Wholesale Corp, will stop accepting AmEx credit cards at U.S. stores from next year. They already did this in Canada so this is not a complete shock. AmEx stock fell as much 7 percent on Thursday, its steepest fall since August 2011. It’s almost impossible that Costco will get rid of credit cards altogether, so most likely they will switch to either Visa or Mastercard. We’ll have to wait and see, maybe some new spending opportunities will arise for those who spend a lot at Costco. I did some of my Business Gold and Platinum spending there. Read more at Reuters.