It's a good idea, and I originally had pretty big aspirations when I implemented the chat feature. We had Yen on as a special guest, but since then we haven't really done much with it (been about 8? months since the chat feature was added). I had a quick chat with Rosenkrieger the other day.
If anybody ever wants to host a chat session, I can add it to the calendar and put in an announcement. The topic doesn't have to be specifically about mantises either. This is a service for members only and since it's not really being utilized for anything other than random (and infrequent) drop-ins, we might as well get something out of it. I think I'm paying like $15/month for it.
Maybe after the calendar contest is wrapped up, I'll hound some people about guest-hosting some chats.
Of course, I don't want to pass up an opportunity to mention that the discussions must remain family-friendly and appropriate for all ages.
I have a handful of people in mind that would make good guests. Keep bugging me about it and I'll make some things happen!