
Not As Bad as ORDB
There was once a popular "service" similar to Spamhaus that black listed servers with open smtp relays. (Where one could use the server to send unauthenticated male from an external domain.) I'd screwed up and left the SMTP open for about a week and they found it and blacklisted us.
Their method wasn't to go after spammers, but against servers who COULD be used by spammers. They would go through MX records and attempt to send spam to themselves and if successful, black list the offending server.
This was rather like walking down the street at night, trying to open doors and when you find one unlocked, publishing a list of them for the crooks to use.