In the retailer/credit card provider relationship, the retailer is winning (Costco, Walmart)

Hot on the heels of Costco's announcement that it would cease its designation of American Express as Costco's exclusive credit card provider and partner with Citi/Visa instead, there's news that the exclusive deal between Green Dot and Walmart may be unraveling.

At the end of its current contract with Green Dot, Walmart is expected to either not renew or vastly restructure the arrangement to cut Green Dot’s commission rate. Either outcome, Seeking Alpha reported, is likely to be quite damaging to Green Dot, which in 2013 relied on Walmart for 64 percent of its total operating revenues and more than of 82 precent of its total units sold.

PYMNTS.COM speculates that Green Dot may continue the deal at a reduced commission, or perhaps some other company may step in as an exclusive or non-exclusive credit card provider. American Express was mentioned. Even if a competing company can't get an exclusive deal, Green Dot would lose some portion of its revenue.

There are some differences between the Costco and Walmart cases. The Green Dot card is a prepaid card, most beneficial to people who do not have bank accounts (Walmart is actively courting this market). Walmart, however, accepts all sorts of other cards - it's just convenient to buy your prepaid card from Walmart. Costco, on the other hand, accepts only one credit card - the American Express card - although you can use any debit card in Costco.

Despite the differences, there is one similarity. In both of these cases, the retailer (Costco, Walmart) is calling the shots, even when dealing with a large company like American Express or Citi.

Or Apple or Google.