In fact, VISA could suffer a lot of blowback if a campaign was organized for people to go to the restaurants that took VISA up on their offer, IGNORE the restaurant's signs, order a large meal and insist on paying with cash. There's literally nothing the restaurant can do about it. It would be a big embarrasment for the campaign and would make at least restaurants (and other establishments that don't take payments up front) wary of signing a pledge not to take cash!!
For those of us who want to fight "on the other side" of the war on cash -- ie to keep it in circulation -- such a campaign would be worthwhile. I, for one would participate. Someone should make a website with a list of the establishments that partnered with VISA on this crap and post it here :)