I dont know that it is really necessary but, it looks like
a fairly clean solutions to me. It might become necessary
as the crowd here grows. Maybe allow multiple selections
in the box to talk to a couple of people at once. Also the
private
messages should probably still be semi-permanent (via the
little check box) to make sure the user gets the message.
> private messages should probably still be semi-permanent (via the little check box)
The friendliest way I thought of solving that was by selecting the user (if s/he isn't already) and submitting an empty talk. It saves you having to check the box(es), and lets you flow through a conversation more naturally, me thinks...