I have run a shoutbox’s before on forums (on and off for a few years, on various forums)
In the long run a shoutbox does more harm than good. lets say if someone has a question and messages in the shoutbox, after a few days the answer to that question will be buried in the archives, and not visible to anyones searches (google or site based).
Without a shoutbox new topics will get made a lot more often and the information is accessible to anyone forever, more people reply and the forum is considerably more active as a result.
I know its cool to have, i used to love the shoutbox but its not going to help us build up our forum activity, sorry dude!