The worst blacklisting service: Spamhaus

Spamhaus sometimes blacklists a range of IP addresses making innocent IP addresses victims of spammers and the incompetence of Spamhaus.  For example, if they find that 123.123.123.1, 123.123.123.2, 123.123.123.3, 123.123.123.4 send spams, they will blacklist all 123.123.123.* IP addresses (i.e. 123.123.123.0/24).  In other words, the collateral damage far bigger than the few bad guys. 

No blacklist is perfect, so Spamhaus's false positive errors are not a big problem per se.  The worst part of Spamhaus is its slow response to no response to requests of unlisting innocent IPs.  It may many days to take an innocent IP off their blacklist, affecting business severely for an extended period of time.  Many services respond to requests for removing innocent IPs from blacklists in minutes.  

Spamhaus is a bad choice for spam blacklists. It hurts legitimate businesses and their customers. Sometimes critical customer support messages cannot reach the recipients.