>     1.)  Cross-posting:  There are (at last count) 39 NetBSD mailing
> lists.  Many messages are of clear interest to more than one list, and
> thus messages are often cross-posted among multiple lists.  A
> members-only restriction on the lists would cause thread fragmentation,
> as each member would get bounced from those lists thehy weren't on
> whenever they hit `reply'.

This is easy to detect, and it's unlikely that a spammer would
cross-post in this way, so you could easily allow cross-posts from any
user through but refuse non-cross-posted messages.

>     2.)  Gateways:  Several sites provide local mail-to-news gateways
> for the NetBSD lists, which both reduces the amount of work the list
> servers have to do, and helps users to keep up with the high volume of
> lists like current-users.  If we had a members-only policy, users at
> these sites would not be able to post questions to any of our lists.

Right.   This is where most of the spam comes from.   Shut 'em down.

>     3.)  Questions from non-members:  A lot of the NetBSD lists exist
> so that users can ask questions about our OS.  It is not odd for a user
> to have a question best directed to a list they are not on.  For example,
> a user who only uses the mac68k port may have a question best answered in
> the more general m68k list, but may not generally be interested in that
> list.

Moderation can easily solve this problem - a message from a non-user
gets forwarded to a moderator, who suffers on behalf of the rest of
us.

>     4)  Try-before-you-buy:  I strongly suspect that if your average newbie
> has to deal with the volume of current-users or even netbsd-users in order
> to get help with an initial install, they are going to go looking for a
> penguin instead...

You obviously don't read Linux mailing lists very much.

One other tactic which might still work is to not put mailing list
names directly on the web page - instead of netbsd-current@netbsd.org
on the web page, you say netbsd-request@netbsd.org.   This has been a
very successful tactic for my mailing lists.

			       _MelloN_