Going forward all merchants have to consider the Groupon/GOOG Offer cost while pricing. They already factor in credit processing - and can't discriminate on Cash customers. eventually a customer paying cash and not using any promos will pay a lot more for the same merchandise.
Actually, that's not true. As of today, because of this[1] $7.2B settlement, merchants will now be able to charge customers that use cards a fee for doing so. This is already the case in Australia as I understand it, and card use has not decreased as a result. I personally use cash for most store/ restaurant purchases (I used to work in the Merchant Acquirer space), so I will finally be getting a better price in addition to reducing my behavior-tracking surface area.
Groupon: How much is a lunch meal?
Restaurant: $10
Groupon: Great, here Ill give you $2.50 for it!
Restaurant: uh.. I'm not so sure about this...
Groupon: Hey customer! Come get this lunch deal. I got a great deal for you, $10 lunch for $5!
Customer: Uh, ok.
Groupon: Sweet! I just pocketed $2.50! Isn't this a great deal!
Restaurant: WTF! I just lost 75% of my gross by doing this with Groupon!