On Mac, Skype Sucks CPU

For past couple of weeks, I have observed that whenever I boot-up the latest version of Skype, my Powerbook 15 starts to get warmer, and fan kicks in more often. Making Skype calls slowed down the whole machine, and for the longest time I could not figure out why. Well, accidentally, using the activity monitor explained why. During a course of a chat with Andy Abramson, I saw that Skype was taking up nearly 27% of the total CPU. In idle state it takes about 4% of the total CPU, versus Gizmo Project that consumes less than half-a-percent of CPU power. Anyone care to explain the technical reasons for this, and if Windows people experience the same CPU-hogging?