Two issues involving unsubscribe

Marc, all:

First off, I'd love to see some unsubscribe links available at
www.postgresq.org/community/lists. Currently you have to drill down via
the archives to get to the unsub links; this confuses a lot of users ( I
know I didn't find it on the first try) and as a result I end up fielding
about a dozen "how do I unsubscribe" questions a week.

Second, (this is for Marc) I'd like to know what's possible in the way of
banning certain addresses from subscribing, either to specific lists or to
all lists. What I want to ban is:
1) anyone from uol.com.br or other domains which use email-back security;
2) certain people who cronically put on vacation notices without suspending
their subscriptions;
3) users like the one today who sent me a profanity-filled request to
unsubscribe.

It seems like majordomo has tools to do some of the above, but they seem to
be per-list only, and to require some knowledge of the filter syntax.
Marc?

--
Josh Berkus