Twitter is a great tool for public relations and a social-media monster that may only grow in audiences and importance. Yet you can pack a lot of trouble in 140 characters. Public figures — actors and rock stars, politicians and professional athletes — have learned this the hard way. There’s no rewind button. So be careful out there. When it doubt, don’t tweet it out.

Take for instance a recent photo tweeted by Russell Brand, a photo of his lovely wife Katy Perry that perhaps was not looking, so lovely at the moment. The shot candid and apparently of her in bed just waking up. He though it was funny and he tweeted it. The photo went viral and made the rounds quickly.