I think it would only be compatible with other mIRC users, wouldn't it?
Take Linux clients, for example. I've not looked greatly in to this subject, but I have read somewhere that the reason video chat isn't (as of yet) incorporated in to IM clients is because of the way the two OS' handle the images from the webcams.
I don't know whether or not this is true, but if it is, I'd say that's a good reason for a webcam feature to not be added.
