I agree with Gomer. Scheduled interviews or topics would be a must for the chat function to be used effectively -- at least one per month. Afterwards, people can stick around and ask questions that weren't in the interview for a while, chat with each other, etc.
After its done, the interview should be posted and, if it is good enough, turned into an article.
I'm all for it if it can be done this way or in some other creative way that will attract people and encourage them to use it,