[squeaky-clean]

Not just lost sales. I've seen a Walmart lose all ability to do credit card sales and after about 5 minutes maybe 10% of people waiting just started leaving with their groceries in their cart and a middle finger raised to the security telling them to stop.

[coldtea]

That's some low class rogue behavior though, not the standard in sales ("they can't process my card, let me take the stuff for free anyway").