We have always been warned of by the un-secured wifi thingie. Since everybody does, we feel it is safe to ignore the alerts.
This is a new tool which puts great sophisticated sniffing tools at the hands of amateur people. To make things simple, this is a firefox extension. If a person installs this, logging into facebook as his next table john-doe is just a click away.
Eric Butler, created this tool, so that he could raise awareness about sites that do not use SSL for their entire content. The problem is not with the free wi-fi, but sites like Facebook and twitter.
Sites like Facebook, and Twitter, uses SSL for just the login part, but not everything on the content. As a result login cookies are transmitted without encryption. If some one else has your login cookie, he can tweet using your account. Thankfully Gmail, has implemented ssl for all their content, earlier this year. So you are good on this.
This is not something new, this has been around for a long time. However, this tool makes it as easy as installing an extension! This is how to fight for your ideas. Write a tool, create awareness, and twitter and Facebook cannot ignore it anymore.