FaceTime for Mac beta was announced at Apple’s Back to the Mac event and shortly after its released it didn’t take long before a shield flaw was found.
Once you’ve logged into FaceTime you can have a look at all the history settings of the used Apple ID. Username, ID, place and birth moment are shown as well as the defense question and the reply to it in a plain text, without another password ask.
After logging out of FaceTime, the password field will still be filled in. Moral of the story: do not use FaceTime on any Mac that is not your personal, password-protected machine. Keep in mind that FaceTime for Mac is technically in beta, so bugs (yes, even safety measure ones) are likely to exist in the software. Apple will probably release an update that fixes that in the near future.
Update: Apple has fixed the safety measure flaw on the server side.