Well, if I was a cafe owner worried about non-customers going nefarious things I would not be happy until IBM deploy a decentralised blockchain solution that anyone with a HTC phone hardware wallet can seamlessly sign in to with the task only taking thirty minutes or so.

Or maybe make it as easy as possible, never changing the password and thereby getting repeat trade. I am sure a firewall can be opted into with the ISP to make sure nobody is downloading ISIS kiddie porn, Trump tweets etc.