The problem with a cashless society is that if all payments are tracked or controlled by a third party, it's impossible to make black market transactions or grey market transactions.

The line between legal and illegal keeps changing, as attitudes in society changes, but not allowing people to vote with their wallets which way society should go is an incredibly bad idea.

How could you run a gay club in a cashless country where it is illegal to be gay? How could you buy marijuana in a cashless state where the legality of it is undefined? How can you donate to wikileaks when no US-based payment provider wants to facilitate payments to it?

The argument against cash is exactly the same as people not caring about their web browsing history being accessible to others, and saying 'they have nothing to hide'.

Well, one day you might have something to hide. For good reasons or bad reasons or whatever, and that's when privacy is a good thing. That's when anonymous cash is a good thing.