This is great news! Adium, the IM of choice for most Mac users, has announced today on their blog that video/audio chat is now available on Adium via a plugin.
Now there is absolutely no other reason to use any other IM application.
P.S. As it turns out it uses a web-based service called MeBeam to do the video chat through your browser, which some users do not approve of as a full solution. Adium commented that this will be a stop gap solution until they come up with the real solution.