I have yahoo. haven't used Mirc in years. the biggest problem I could see with live chat would be keeping trolls & other disruptors at bay. I'd imagine it would be a mod's nightmare.
I usually don't chat online much, but when i do want to chat, I'm always looking for like-minded people. I like to separate the wheat from the chaff so to speak. And as for trolls, its always fun to watch them get torn apart by FReepers- or anyone with an IQ above 23.