According to Justin Mason, domain registrar (and email/web hoster) Godaddy is misusing the Spamhaus PBL: Using it as a URL filter. This is where you convert a URL hostname to its IP address, then look up that IP address (or its nameserver) on an IP-based blacklist. Great idea. I do it with the SBL. It's a horribly bad idea for the PBL, though, because the PBL is not meant to be a list of things that aren't allowed to have web servers. Using it this way is going to cause false positives like mad.