Requests for comment/Exposure of user IP addresses

This request for comments is regarding exposure of user IP addresses.

Previous discussion
[FIXME: there have been a million wikitech-l discussions about this; find and cross-reference here please]

Background
Currently within MediaWiki, if a user chooses not to log in, MediaWiki uses their assigned IP address as the user identifier. If a user edits while logged out, the IP address is recorded and stored in perpetuity as a username would be.

Advantages to using IP addresses

 * Knowing whether an IP address belongs to a school or the U.S. Congress or whatever can be helpful information.
 * IP addresses are relatively difficult to change for an average user, helping prevent vandalism and other repetitive harm to the projects.
 * IP address ranges can be blocked.

Disadvantages to using IP addresses

 * Privacy concerns!

Proposals
Related to the previous discussion above. Usually some kind of salting, random name thing.