According to GigaOM, over 27 million users were signed into Skype at the same time yesterday, up from the average 25 million. Skype hasn't come out and said outright that these were the contributing reasons, but it would only make sense if users were trying the features out. It would seem odd for that many more people to be making regular Skype chat calls on an ordinary Monday.
Have you started using either the iPhone video chat app or the new group video calling packages? Or both?