An actual conversation overheard on the local Exchange Server (only the names have been changed to protect the innocent):

From: Smart-a$$ Australian 
Sent: Thursday, 17 January 2008 12:58 PM
To: PIFEM Practitioners
Subject: RE: STOP REPLY ALL

Hahaha, I am so blogging this!

From: Jim
Sent: Thursday, 17 January 2008 10:01 AM
To: <A really big distribution list> <another list that might find this funny>
Subject: RE: STOP REPLY ALL

Save the bits!!

From: Harry
Sent: Wednesday, January 16, 2008 3:00 PM
To: <A really big distribution list> <another list that might find this funny>
Subject: RE: STOP REPLY ALL

Yours is #7.

Guys – just your Stop replying mails hav resulted in extra 6 mails !

From: Laura
Sent: Thursday, 17 January 2008 9:53 AM
To: <A really big distribution list>
Subject: RE: STOP REPLY ALL

Me too. Please stop reply all now….

From: Bill
Sent: Wednesday, January 16, 2008 2:52 PM
To: <A really big distribution list>
Subject: RE: STOP REPLY ALL

I also agree stop reply all

From: Sam
Sent: Wednesday, January 16, 2008 3:50 PM
To: <A really big distribution list>
Subject: RE: STOP REPLY ALL

I agree stop reply all

From: Henry
Sent: Wednesday, January 16, 2008 4:58 PM
To: <A really big distribution list>
Subject: STOP REPLY ALL

STOP REPLY ALL

I think I am going to recommend a feature for Exchange vNext for "enforceable email etiquette rules". A penalty like:

Your outgoing messages have been suspended for 45 mins. Reason: Failed email humour attempt costing the equivalent of 100 work hours. In future, try to be funny to a smaller group of people first, before graduating to the major league.