There are many open "free" networks around- in some airport lounges, in coffee shops, bookstores, etc.
When connectivity is available, it seems tempting to sign into Facebook, or Twitter to update status or see what is going on. But last year, there was an article about firesheep and other similar applications that could be used to sniff data and allow another person to potentailly capture the login / passwords of those around them.
How prevalent is this danger and what actions can we take to protect ourselves other than just not using open networks?
The article discusses how cookies can be captured OTA (Over the Air). The only true way to get around this is to use a secured connection ( an https:// connection) when going through any Social Networking site i.e: Facebook, Twitter, Google+, etc,since data is streamed or transferred through a TLS/SSL (Transport Layer Security/Secure Socket Layer). Also, try to find a Public Connection with a higher level of Wi-Fi security or authentication using WPA2 with an AES encryption standard.
Make sure that when you are on a Public Network any File and Printer Sharing and Network Discovery is disabled. In Windows 7, the Network Location Awareness (NLA) feature found in the Network and Sharing Center does this automatically on Public Networks if the settings were left on default.
In most browsers right now, there's an option to disallow websites to track your location. All the better will be to use InPrivate browsing when in IE, Incognito when in Google Chrome or Private Browsing in Firefox, these modes will not keep any session cookies without you worrying to delete them manually once you close the browser.