Well, I finally had my first run in with MIPSpace. Needless to say it was very annoying. You can find their web site at http://www.mipspace.com. Their motto is that users have the right to block everything (Actually, it's "Why can't users just say NO?") The problem with a user being able to add IP addresses to a public database that will block access to email from that IP for everyone else who uses the service is simply wrong. Of course, they will argue, based on their motto, that I am wrong and so we have a difference of opinion.
The problem becomes even more pronounced when the avenue for correcting issues can only be done by the owner's of the IP. The suggest that you have your IP addresses SWIP'd to you, which can't be done by Tier 2 or Tier 3 providers and even most Tier 1 providers won't do it because of the transient use of the IP addresses. Say if I'm getting my service through FiOS. Verizon will not SWIP the IP address groups to the end user, so I'd have to go get Verizon to tell MIPSpace that I'm not a bulk email marketing provider??? So, apparently, you can easily get on the list, but getting off is retardedly impossible.
The service that adds this list is at http://www.linuxmagic.com which provides a IP address reputation service. MIPspace is just one of the sources they use to come up with a reputation. I'm sure they provide a "score" of sorts, so if only one of the sources they use marks you as a bad reputation you might still consider getting email from that source. That leaves it up to the email administrator. My experience is, never just accept the resource's decision on what is bad and what is good.
So, while I think MIPspace is off it's rocker, it is ultimately up to the email administrator to determine what gets into the mail system. And even then, it would be wise to allow the users to set their own white lists.