From Russell Beattie comes his advice tacked on to the blogger policy for employees at Yahoo! (link to pdf file).
My favourite line:
Okay, all that said, try not to be dumb about being a Yahoo! Blogger , hey? Write about what you do, not about what you're doing, and don't write about anything you would normally lower your voice to talk about in a public place. This stuff is fun, and not being a bonehead will keep it that way. :-)
That reminds me of the standard look around the room thing that I do when I'm talking about work when in public. You can never be too sure who might be around that might hear something you don't want them to.