Russ has hit the nail on the head

>because people are
including all the previous messages at the bottoms of their new
postings, so that bottom banners multiply exponentially.

No sure what this means

>If the latter, I guess the only recourse is fulmination, but I
don't think it will work.  

Again spot on

>People simply _don't look_ down below
the bottom edge of their monitor screen.  What's down there
doesn't exist for them. Out of sight, out of mind.

Does anybody know how to stop it without shouting at list subscribers

Susanne