I'm only saying this because I was a mod on a forum that had both the shoutbox, and the additional off and on-topic disucssion areas...

...moderating the shoutbox takes much more work from the side of volunteers. There very little control, and streams of conversations are harder for most users to keep along with.

The better solution is and would be for the entire board to be something akin to Google Wave; where you can have the "river of conversations" discussions, and the forks into the targeted conversations throughout. I'm not sure that such a thing is coming to Talk.Maemo, but in light of this suggestion for a shoutbox, would be a more senseable solution.