After a quick look over of bitmessage, it's something that I would have to install and configure and check from time to time. It seems to me that we would want to have a communications medium that everyone already has....such as email. I don't need to set up yet another account and have to check yet another source (facebook, twitter, linkedin, email, forum posts and then add bitmessage on top of that).
Just my BTC.02
Thanks for your thoughts. Email is the obvious choice and, of course, is fine for us, but I appreciate that some people would like to protect their anonymity more than this. Ideally, we're looking for a single solution that everybody agrees on, which makes it easy for us to contact everybody at the same time. If this isn't possible, then we can use a couple (e.g. bitmessage + email) of approaches, but probably no more than this or it gets too unwieldy.