Skype 4.2 and newer versions will minimize to the Windows 7 Taskbar rather the System Tray or Notification Area, when you press the Minimize or the close button.
Its not that bad but sometimes its just annoying to leave Skype running in the Windows 7 Taskbar. And its not that useful for the most users. Most of the time you may end up pressing the Skype icon on the Windows 7 Taskbar when you didn’t intent to.
By default Skype disables the option of Minimizing Skype to Windows 7 Taskbar but it can be easily fixed.