I have the same issue and have tested with 3 different MacBook Airs. All running the latest OSX (ML 10.8), Lync 2011 (14.2), O365 accounts, each Mac different HW releases (early 2011, mid 2011, mid 2012).
Video calls from the MacBook Airs DO NOT work. If the person you are connecting to is a PC user, you can see them but your camera will not work.
Here is the error message received on all MacBook Air/Lync 2011 client when trying to make a video call:
" Your webcam is not available. Make sure that your webcam is correctly configured and is not being used by another application. Then start the call again."
There are no other applications using the webcam and there are no settings available to configure the webcam from Lync. Video calls work from from all other installed video presence applications.
Any and all help is greatly appreciated!
-Robbie