First rule of Bitcoin: keep your private key safe.
When Bloomberg TV news anchor Matt Miller presented two other anchors with $20 each of Bitcoins during their "12 Days Of Bitcoin" segment, he accidentally flashed a QR code that was meant to be kept private. The QR code being displayed on screen allowed Reddit user "milkywaymasta" to enter the account and take the $20 of Bitcoin (think of the QR code private key as a bank account and PIN number.) The user then went on Reddit to take responsibility for the theft.
Once word made it back to Miller about where the Bitcoins had gone, he decided not to pursue it further, writing: "so freaking classic but also a GREAT lesson in bitcoin security! you can keep the $20 -- well earned."
Remember, just because a currency may be digital, doesn't mean it can't be stolen. Learn the rules before you play the game.
[via Business Insider]