The theory is that this move will protect children. I susupect cost might have a thing or two to do with it. The costs of running the chat servers must be considerable, and Microsoft has not been slow to start to try to make money from Internet services (the extra for-pay services added to Hotmail, for example). According to the New York Times, Microsoft's key competitors will not be axing chat. For AOL, the chats are private to subscribers anyway. But Yahoo apparently has no plans to charge. We'll see what happens!