They may look like an average Joe, but the person sitting next to you at the coffee shop could be hacking into your online accounts. A new program makes you susceptible to snoopers while using shared Wi-Fi networks. Think computer hackers are the only ones who can break into your online accounts? Think again. A simple software called Firesheep lets just about anyone steal your identity online while using Wi-Fi in a public place.   Firesheep is a free add-on that lets hackers break into your Facebook, Gmail, Twitter, or any other online account you have. And the fact that it’s been downloaded…