Just don't forget that any messages you post in someone's profile messages (which I guess started the same time as the friends feature), anyone can see it.
Also, something a few people might not know (at least from my observations--not that I'm checking!) is that if someone leaves you a message in your profile messages, and you want to respond, you have to click on the "open conversation with..." link first. Otherwise they will only see your response if they check
your messages.

Barbara