That's an idea - purge it if not updated.  If you are worried about defamantion, slander, etc. - just factual information would refrain from all that such as the following:

Current Date, Name of Company, Date of Invoice, Amount Owed

Nothing Else - you would be able to see by looking at the current date versus the date due how much the invoice was overdue and the amount - if multiple invoices you could put a range of dates, etc.  The one that went around Dallas a couple of years ago I never participated in but they also put the case number if they have filed suit against them.  I guess we could add the Company that is owed to the list above and a contact # because that is what they did so anyone could call them if they had a question.