One of the most "ugly" things about the new chatter / email system is that some informations are just not reliable:
One of the worst examples for me is that if i send an e-mail lets say for an opportunity and some of the followers are set to "Receive Messages by Email: Never" they will not get an E-Mail. But you can not see this!!!
This may sound ok BUT you will see in the message that this E-Mail was send to the followers - wich is WRONG - so you would have to "Check" for every send E-mail what the setting of "Receive Messages by Email" every follower is at the moment when you send the E-Mail - That's just not usable !!!
My Suggestion:
1.) If a Partner is set to "Receive Messages by Email: never" do not automatically add this user or partner as a follower!
2.) If a Partner is already a Follower but set to "Receive Messages by Email: never" it should be reflected in the send message! So if i look at an E-Mail there should only be the REAL Recepients listed!
3.) Why not add checkboxes for all Followers when you compose an E-Mail with OpenERP - this way you could set or unset the recipients very selectively.
Number #3 sound like a reasonable suggestion!