Two years ago, Visa U.S.A. Inc. conceded a hefty $3 billion to settle antitrust allegations with retailers over its "honor all cards" policy that forced stores to accept debit cards and pay higher processing fees. Plaintiffs' lawyers nationwide have been quick to follow with a spate of similar "indirect purchaser" lawsuits on behalf of consumers. But courts have been largely inhospitable, finding that Visa and MasterCard's relationship to consumers is too tenuous to support antitrust claims.
Details here from the National Law Journal via Law.com.