On the show a few weeks ago we profiled the Firefox Browser extension Firesheep. It allows users to steal your unsecured Facebook login information over open Wi-fi networks. This means that if you're on an open network at a coffee shop somewhere, it's likely that you're vulnerable.
In case you wanted fight against this threat, you now have a few choices.
The Electronic Frontier Foundation released HTTPS everywhere, which forces an encrypted login each time.
Then there's Blacksheep, which simply blocks the Firesheep plugin from working.