ok i have my own entheogen site and i do have a chat app on it - it did draw info away from the forums as its much easier for ppl to just pop in and ask a q but that has been sorted out - questions are kept to the forums and the chat is for just chatting and getting to know other members.
If controlled properly i dont forsee it being a problem, but that doesnt mean someone needs to be there to control it, ppl on my site are able to govern themselves and im sure it would be the same here - perhaps a test run is a good idea - just for a week or so - if it fails it can be removed - if it works out well im sure it would be much appreciated.