I worked somewhere where overdue accounts were left to sit. We continued to serve these people – often as premium customers. When I really became aware of the situation I sat with the accountant and worked out a system that would stop bad debt. The system recovered two of the worst offenders in two days.
Interestingly when the boss came back from overseas she let the system go and debts ran up again.
I have to wonder at the will or mindset that allows (encourages) others to abuse so badly.