Mark Zuckerberg posted a photo of himself holding up a cardboard Instagram post prop in celebration of Facebook-owned service now being used by more than 500 million people every month. Zuckerberg said in a Q&A with students that he puts a piece of tape over the webcam on his personal laptop. The Facebook CEO also apparently tapes his microphone, too, in the background of a laptop with a piece of tape over the built-in camera. He’s got cause for being paranoid after account hijackings and malware attacks.”]