I think it's limited to 10 users at a time, not 10 total users. Unless I read it wrong. I've never used it though. Quoted from their site
"Take advantage of the opportunity to share any screen content or application over the Internet in true color quality with up to 10 participants simultaneously, while still sitting at your desk."
I might try this just for the heck of it.
From their forum: It is not possible to start more than 1 session as organizer. However, you can ask the second person to start the session and you can join. Then he only needs to grant you remote control.