Skype Video Call Kills MacBook Pro Battery in less than 1.5 Hours Running OS X Lion

Last night's Skype video session, running in a window (not full screen), redded my battery gage in under an hour and a half's time on Mac OS X Lion.

The battery in the MacBook Pro is rate to run 8 to 10 hours. How is it that Skype can absorb such an immense amount of power?