Maybe not all of them but the ones I have heard about do not attempt to verify the report made to them, allow personal information about clients to be openly posted, and sometimes even refuse to ever take a report down even if it is shown that the information is false.

So, just how useful are such sites when clients are being blacklisted for minor offenses? Not very.  And yes, they do leak; even if a site attempts to verify that providers are legit information will get out.  A provider that would blacklist someone over a miscommunication like this one or an NCNS is someone I would not choose to see.  Word does get around about which providers do this sort of thing.