Are blacklists legal, ethical, etc?

Blacklists came about as a response to unethical and illegal spam.  Blacklists have no other purpose but to stop bad or malicious acts, so they typically occupy the ethical high ground. Since they are used by businesses, universities and internet service providers to screen traffic, they are incented to be ethical, list only known bad actors and not list legitimate commercial traffic.  To do otherwise would undermine the value of their service to their own customers.

All that said, MxToolbox carefully curates a list of the most used and best maintained blacklists.  All the blacklists we check provide free delisting services.  We feel that requiring payment for delisting is not ethical.  However, a few blacklists offer expedited delisting services, which is a bit of a grey area.  Other blacklists may ask strange or seemingly random questions.  Think of this as geeks being geeks, rather than anything malicious or unethical.