Keep in mind the amount of monetization that occurs around purchase data in the present system. The ease with which you can associate transactions to real identities isn't even comparable.

What monetisation ?

The bank isn't authorised to provide that information to third parties.

Are you confusing the spirit of the law with the letter of the law? Or do you really think that banks aren't selling your transaction data?

http://www.cardlytics.com/technology/

Despite the "firewall" between the bank and the marketers, information is being sold - it just requires an extra step on the part of the marketers (leaving the banks legally in the clear).

That's beside the point. The parent was simply asking what use exists for an anonymous currency.