After struggling to see the benefit of Skype 5, I wished to downgrade back to the previous version. However, I couldn't find a link anywhere on the Skype.com website for previous versions. As a result I searched on Google and found a third-party website offering previous versions for download (http://mac.oldapps.com/skype.php?old_skype=37).
I downloaded and installed the older version, and logged into my account. Later that night I received an email from Skype confirming a purchase for an "Online Number" that I hadn't made. I immediately logged in to investigate and I could see the transaction pending. I managed to log into Paypal and remove Skype from my trusted billers in time.
I believe that the version of Skype I downloaded was stealing login credentials. Let this be a warning to others that are trying to roll back their Skype client!
I emailed Skype's security team (after long minutes trying to find a very hidden contact link on their site). The response was cookie cutter, but ridiculously contained a sales pitch for the very feature that was just illegally purchased from my stolen account! This was infuriating - like a slap in the face from Skype considering my state of mind:
<i>If you'd like to get more out of Skype, why not learn about all our great features - like Online Numbers? Anyone can dial your Online Number from any phone or mobile, your Skype rings and you pick up the call – wherever you are in the world. Find out more at http://www.skype.com/go/onlinenumber/</i>;