For small forums, they are okay. But they definitely aren't professional, and they definitely do not belong on a forum where shouts will be near-constant and fill the database up with useless crap. We get thousands upon thousands of posts per day. No need to get dozens of thousands of shouts per day.
Well, a shoutbox brings out lurkers who never post. Add to that people like to spam the shoutbox (double, triple, quadruple, etc. although it could be fixed), I'm sure there would be at least 8,000 a day. Ya.
What I don't like about shoutboxes is it tends to take away discussion from the actual forums. People tend to just ramble on the shoutbox, and not post much on the rest of the forums. Swear it's true. Happened with EOW, right. BB had one, and there were hardly any posts, but plenty of shouts. true