I have no idea what Skype was thinking with version 5 of their client. It is atrocious. There is so much white space, if your Instant Messenger client takes up more screen space than a web browser, you're probably doing something wrong. Download version 2.8 - http://mac.oldapps.com/skype.php
Skype never made good client software for apple's devices, so it's not surprising. All versions have major UX flaws and iphone app is very buggy and slow/freezing for example.
It's horrible design, and I can't help but think that no one at Skype has actually used it for anything, which seems improbable. I've heard that the Android version does the same thing as well. It's just terrible.