On my (Moderated) list  BALT-L I take the line that if an event I hear about
is news to me its likley to be news to my readers.
 
I collect short queries, replies and announcements for collation in
a single message two or three times a week and include such 'commercial'
material in the section "announcements" sometimes headed with a line saying
' Commercial information distributed as a public service '.
 
That gets the information across and guards against repeat bombardments,
allegations of endorsement etc...
 
How does this strike other owmers?
 
(Where a controversial thread emerges I sometimes find it useful to
collate several short messages in the thread into one 'magazine'
message. Advantage - readers see several points of view at one go and
are perhaps less likely to jump for the reply key...)
 
Edis Bevan