Since late 2002, I have used an email signature hack to explicitly tag the privacy of a thread:
this email is: [ ] blogable [ x ] ask first [ ] private
Phil Wolff was the first to pick it up and by now it's likely you have seen it in email or on the web, even usenet.
It works because [ x ] ask first is the default. I've only had two cases where someone didn't respect the privacy tagging of the email and blogged something.
Now I've made it easier to change to [ x ] blogable (sometimes bloggable) or [ x ] private through three different email signatures. For Mac users, click on the images for a how to in Mail.app preferences.
It gives you the ability to select the requested privacy through a pull down bar.
Just click, drag and cover your ass. Or do the same to promote it.
UPDATE: What email hacks can you think of? Merlin Mann gave me three off the cuff suggestions. Let's collect a few on this wiki page and then contribute it to the 43 Folders wiki.
