in reply to 24Hr log of chatterbox
Logged chattering could lose context. Context is not just a factor of date/time, which can easily be logged (although which time zone would be used?), but also can relate to activity on the site (recent postings, who is logged in at the time) or events outside of the site.
For example, if someone made a post and failed to use code tags, I might mention that on chatterbox (without using msg if that person were the only person logged on). The person doesn't reply but fixes the post. This is a boring example. Who cares about some missing code tags?
Next the person writes something insulting me for even bringing the code tags up (or a poem talking about how wonderful I am for mentioning it, depending on what view of human nature you prefer in examples). I'm tired, so I say more than I might have otherwise--"You are so rude. I wish someone would rm you." (alternate: "Please remove that, it's embarassing!"). Point having been made, the person changes the text of the node so that it says "Oops, sorry for the blank message, please remove this." Three hours later, it gets removed. Seven hours later someone looks at the log and wonders what I'm on and whom I was talking to.
I know, these are silly examples because nobody really cares what I was saying to the unknown person at 2 in the morning. Which is exactly my point: if it's important, it belongs in a node; if it's in the chatterbox, it's probably disposable (and if it isn't, someone should write it up in a node so it will be saved).