[This is my earlier private message , I want to share it with the list as it clarifies some of my intentions on filtering. Let me know what you think...]
One of the difficulties with multiple lists is cross-posting. It's often not easy to find a particular category for any particular message. (that is not to say it shouldn't be done).
What I would suggest to implement, at the first stage, is simple programmable filters that could be used as optional extensions to the existing list and/or Web message repository. Nobody would object to them - if you don't want to use it the filters, you don't even see them.
The filter would represent a user-configurable set of selection directives that can be defined through a web form. The directives would define the posters, topics, and other search criteria that the user would or would not like to see. You could also just use somebody else's filter (if you were allowed). For example, I could subscribe to Greg's public Investment filter, plus exi-member filter, plus all messages specifically approved by Max or Brian. Dr. Newbie might subscribe to the Basics selector except for messages marked by either of the ExI directors as junk, plus everything prefixed with MED:.
This is relatively easy to implement and to use, and will lead to appearance of alternative private moderators (quite extropian, IMO), with undivided message base. , and no issues with duplication and cross-posting of messages, coercion, common denominators, etc.
We could probably cooperate with CritSuit (see crit.org) for some of the features.
On further stages, we could implement reputations, real collaborative filtering, and other more complex functions.