People Who Type to See Their Thoughts in Writing

I am on several sites where you can do live chat. I have found that many chatters like to type even if noone wnats to hear or read what they have to say. How do you tell them to shut up nicely? I have yet to figure it out, so I just keep talking with the other people in the room blowing over the 'big mouth'. Even then they try to put in their tw cents worth.