Be careful what you wish of is an old saying that may be applicable to the recent proposed settlement of a long anti-trust dispute between retailers and the major card brands and some major card issuers.

Under the terms of the settlement, Visa and MasterCard along with some of the biggest card issuers will pay retailers a total of roughly $8.25 billion. The settlement also allows for retailers to surcharge, with certain restrictions, consumers who choose to pay with a credit card.

But the settlement only becomes official if enough retailers sign on to it, and there are indications that whether to sign or not is becoming an issue for some retailers.

The Merchant Payments Coalition, an association or retail groups organized to take positions on card interchange, has been reminding media outlets that not all retailers are keen on the agreement and that it only becomes final if enough agree.

According to media reports that that MPC has been referencing, small merchants in particular are expressing concern about the surcharging provision of the agreement, pointing out that agreeing to surcharge card transactions will put them at a disadvantage, perhaps a crucial disadvantage, with other retailers who decide not to surcharge.