If you use Fring, the Skype client for the iPhone, iPod Touch and numerous other mobile phones, have a look at your Skype privacy settings after using Fring. You will probably find that all your incoming settings have been reset to "Anyone" can contact you for both chats and calls, no matter what you set before. This gets reset every time you run Fring to use your Skype account -- you don't actually have to do anything, just Fring starting up and logging into your account to display your active buddies is enough.
I've been getting a lot of Skype spam chats ("Hello Dear...") and I finally discovered that Fring is the culprit that's opening Skype up. There have been a lot of angry messages on the Fring forum but the Fring programmers don't seem to have responded yet.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic