One of the features in Mac OSX is something called 'Back to my Mac'. It's a service whereby you can connect to your computer from a different computer. The idea is that you can access that file you left at home from wherever you are. Well, a laptop was stolen - and the owner decided to use the 'Back to My Mac' service and watched the thief using their computer. They used the in-built webcam to take a photograph of the thief, who was known to a room-mate of the victim.
The thief realised what was happening, but by the time they covered the webcam it was too late.
Of course, all of this could have been done with Win or Linux, but not in quite as user-friendly a way.