The NetWar book analyses the Burma mailing list as an example.
People that don't unsubscribe by using the correct procedure are subscribed to another mailing list that keeps sending them some pointers until they manage to unsubscribe.
Yes, in the old days of the Internet this was a dangerous place full of ol' wizards that would zap you for being a foolish newbie. These days, we are slowly getting used to non-techie people making foolish mistakes. But instead of educating them (as is still required for the old mailing-list technology), we offer SimpleInterfaces.
One problem that mailing lists have (that wikis can help with) is the need to rehash old discussions every now and then.
Another problem (that wikis only partially overcome) is the tension between too much or too little information -- i.e. if you have something that may be interesting to the list, should you post it (adding to traffic), or not post it (with the probability that some members of the list will miss something)? On mailing lists, people can glance over the subject headings to decide if they want to read a message. On wikis, messages are posted to individual pages, and people can glance over RecentChanges and decide what to read. The wiki method is more effective because the meanings/topics of particular wiki pages become well-defined over time. That is, the page upon which something is posted (combined with the summary field) often gives more information than most email subject headings.
With ThreadingForWiki, we could do even better than this; it would be possible for each message to be specific to a wiki page, to have a "thread subject line" (analogous to the subject line in email), and also a summary field (analogous to the summary field in wikis)
Another difference between mailing lists and wikis is that in some small mailing lists there is an implicit expectation that all members be familiar with every message that is sent to the list while they are a member.
See also ReplyToMunging
One of the most interesting properties of mailing lists is that they're a technology that everybody understands.
When you're at an activist conference, with 80-120 people there, all powerful and capable, but half grossly incapable of operating even the simplest bulletin board system online, there is only one option available: the humble mailing list.
Even then, people must often be force-subscribed to lists, because they cannot figure out how to subscribe to a "-firstname.lastname@example.org" address.
But once force subscribed, these people do understand how to read and send e-mail, and read and send e-mail, they do.