Quoting Steve Litt (slitt@???):

> A mailing list is like vendors shipping to your house.
>
> Forums are like calling 15 stores to see whether they have any orders
> for you yet.

I may have to FAQ this on my Web site, because it keeps coming up.

1. There are far greater social and technical factors that motivate /
create an incentive towards strong, centralised content control on Web
forums, with the result that regimes of active moderation and
retromoderation are much more common, hence the result tends to be
more strongly stifled by the admins than on mailing lists. (I can
picture my friend Steve Litt rising to complain about debian-user,
and can only say 'Hold that thought, Steve.')

2. In particular, because on Web forums there is (typically) nothing
anywhere near as effective as are killfiles (old school, e.g., mutt) or
scorefiles (new school, e.g., emacs Gnus) available to participants to
avoid seeing what/who annoys them, instead the forum admins are under
greater social pressure to enforce social conformity against everyone,
with stifling results.

In case the contrast between the two models is not obvious, note this
statement of policy at Silicon Valley Linux User Group for its mailing
lists, which may be a more stark expression of attitude than most but
I would maintain reflects an ethos common among mailing list admins:

SVLUGs' listadmins normally intervene only to ensure lists' technical
operation, to halt spam (incontrovertible spam, not postings someone
merely dislikes), and to halt major eruptions of offtopic spew.
Enforcement if any should always be minimal and public. (We don't do
backroom politics, and our preferred means of social control is to help
everyone apply his/her own well-tuned killfile.)

http://www.svlug.org/policies/list-policy.php

(Necessary disclaimer: I wrote that, codifying consensus among the
active volunteers and SVLUG tradition.)


3. It is relatively difficult (or at least requires non-default
anticipatory action) to independently preserve local copies of one's Web
forum postings against the (strong) possibility of that Web forum
folding up its tent in the night and disappearing. By contrast, I
still have automatically made archival copies of my outgoing posts to
mailing lists and newsgroups going all the way back to the 1980s, and
have in some cases HTMLised those a decade or two later to create
articles for my http://linuxmafia.com/kb/ knowledgebase. By contrast,
the Web forum posts I've lavished time on since the mid-1990s have
pretty nearly all vanished when those forums suddenly went away without
advance notice.

4. Which reminds me: Web forums have over the decades since the 1990s
tended, disproportionately to get clobbered (to suddenly die, to vanish
off the Web, to go 'Poof!') without notice. Sometimes, this is caused
by a corporation hiring some new Web weenie who decides to make a name
for himself/herself by jettisoning everything the prior Web weenie did
including choice of Web forum software -- and the new Web weenie feels
not the slightest obligation to port over to the new implementation
anything people posted to the existing forums. That's merely 'Web
content', and, if the suckers who wrote that valued what they wrote, why
did they post it onto a corporation's proprietary forum without charge?
So, all existing content gets blown away without a second thought.
Denizens of InfoWorld Electric went through this process twice before
some of us learned the obvious lesson. The third iteration was a
ghost-town. (I'm sure Web weenie #3 trotted out a fluent excuse for
IDG/Infoworld management, explaining the sudden lack of participants +
traffic.)

In that regard, it's probably significant that it's pretty easy to carry
forward archives and membership rosters from one host to its replacement
or from (e.g.) majordomo to Sympa to Mailman, because the underlying
data formats are stable and commoditised. Web forums, not.

5. Web forums have poor presence in Web search prominence and archives
like Wayback Machine / Internet Archive. (In fairness and in contrast,
crowdsourced knowledgebase sites like StackExchange are uncommonly good
in those areas.)

6. In part because of the relative difficulty of preserving local
copies of one's posts, in part because of the no-killfiles problem,
and in part because of the webmasters-blowing-everything-away problem,
and in part because of poor search presence, experienced computer users
are more likely than not to prefer mailing lists / newsgroups over Web
forums, which in turn impairs the latter's percentage of well-informed
users _in general_ (with honourable exceptions such as, I assume,
http://dev1galaxy.org/ ). Which in turn is a further disincentive for
experienced users to participate.

7. Mailing lists and newsgroups benefit, substantially from an
established user culture that pretty well supports substantive
discussion. Web forums, not so well.

All IMO and in my experience, of course.