Sen. Dick Durbin (D–Ill.) has been going after frequent flyer programs. If he can delegitimize them, he's got a better argument against opponents of his attempts to regulate credit card swipe fees if they respond "But my miles!" (A majority of frequent flyer miles are earned through airline co-brand credit cards.)

Durbin, along with Sen. Roger Marshall (R–Kan.), seeks to limit the amount that merchant processing networks such as Visa and Mastercard charge to retail businesses. Rather than imposing a direct price cap, their current Credit Card Competition Act ¹ would require banks to offer merchants a choice between at least two unaffiliated networks when processing credit card transactions. This means a Visa-branded card issued by a bank could no longer exclusively route transactions through Visa's network alone; it would have to provide at least one alternative network to process the payment.

Banks pay airlines for miles, and they rebate a portion (sometimes all) of the credit card swipe fees to consumers to encourage transactions on their product. That helps them generate charge volume and attract consumer lending. Customers who pay their bill in full each month come out the best: They get the rebate without giving the bank interest on revolving balances. Lower card swipe fees mean less valuable rewards.