Bug or not? Windows CardSpace disables Aero Glass

Snooping around the Control Panel ended up in clicking on something that appeared new to my eyes: Windows CardSpace. What is it? I am not quite sure and i don't care enough about it at the moment since it didn't really make any news lately. More information about it can be found on Microsoft's Windows Vista Help website.

The intriguing part about it is that it seems to disable the Aero Glass interface when it is launched; in a manner similar to other programs that are not entirely compatible with Vista. Since it is a default piece of software built into Vista, shouldn't it be compatible with Vista?