You said one thing that caught my attention. You said the merchants are pawns, implying that they have no choice. I will test your theory. Is any merchant forced to take credit or debit? No, they can take cash or cheque, but they choose not to because they know deep down that cash and cheque are far more expensive than debit or credit. That's why they're taking it.
On June 9th, 2009. See this statement in context.