Of course in my mind the chatterbox and the /msg's are two completely seperate things.
Personal messages, with that tell-tale check-box like an alarm siren screaming in your face, are rather hard to miss. The 'Chatterbox' itself on the other hand, is quite easy to completely ignore.
I myself have the chatterbox placed at the very top of my sidebar, so that I can easily see new /msg's, though I rarely read (or write to) the actual chatterbox. (In a desperate attempt to reduce the already extreme amount of time I
waste spend noding.)
In any case, it's a good idea to keep a tab on your personal messages, wherever your chatterbox is located.