There is an option in Exchange System Manager to prevent or allow Out of Office messages to be sent to external addresses. Technically, this is pretty easy to configure - and Exchange 2007+ lets you set a different message for internal and external use - but the question I have today is whether it's a good idea.
My manager asked what is "best practice" on this. I think the answer is that there are arguments both ways and have detailed some to him, but I suspect there are other reasons that I haven't yet thought of.
I'll create two answers; one for "yes, let people do it" and the other for "no, no, no, this is a terrible idea" and put in the reasons I can think of. Can I ask other people to edit in any more arguments they can think of?