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With Messages, you and a friend with Mac OS X v10.5 Leopard or later can share a screen, even at a distance, making it easy to collaborate on a project.
You and your friend can do anything on the shared desktop, such as opening folders, creating documents, and copying files by dragging them from one desktop to another.
During screen sharing, Messages automatically starts an audio chat so that you can talk to your friend.
You can share screens using AIM, Jabber, Google Talk, and Bonjour. You can’t share screens using iMessage or Yahoo!.
Screen sharing in Messages is independent of screen sharing settings in System Preferences. You can share screens using Messages even when Screen Sharing is deselected in the Sharing pane of System Preferences.
Important: When you share your screen with a friend, your friend has the same access to your computer that you have. Share your screen only with people you trust, and be particularly careful if you receive a request to share your screen from someone who isn’t in your buddy list. If the request comes from someone using Bonjour, remember that the name shown for the person in Bonjour does not necessarily match the person’s real name, so his or her identity is uncertain.