After some investigation, we have found that the OSX 10.8.5 update is missing a specific file that would allow some apps such as Skype or iMovie to access the built-in facetime camera on Mid-2013 MacBook Airs.
At this point, we are not sure how this can be fixed, and we'll get in touch with Apple to see how we can solve this.
From our tests, however, external webcams should work. It's not the best workaround, but until something gets fixed, that is the only known (and hopefuly temporary) solution.
For the more tech-savvy readers:
The 10.8.5 update updated a CoreMediaIO plugin that accesses the MBA camera, but didn't bundle the 32-bits version of it.
Other (older and newer) versions of the OS do include a universal version (32 and 64 bits), but not 10.8.5.
This means 32-bits apps such as Skype or iMovie cannot load the plugin, making the built-in facetime camera invisible to these them.
I spoke to Apple senior techs, of course they are oblivious and no known fix. I really need to learn my lesson and STOP updating to the latest OS when it comes out. I will say that I am a bit shocked though that it appears Apple may be forcing the hands of developers like Microsoft and Google to get their apps up to 64 bit or they simply will not work. I use Skype every single day, now I can not use it at all, unless from my cell phone... What is everyone's thoughts on this. Was this an "oops", or was this intentional on Apple's part?
Apple has know about this issue since June. There are many applications that don't work with the FaceTime camera. See the KB article from June.http://support.apple.com/kb/TS4552
They say go to the developer for a resolution, it's not Apple's problem. Is Skype going to fix the problem? Otherwise, cancel those orders for MB Airs. There's no way to video chat with folks on PCs, so time to order some netbooks!
MacBook Air (Mid 2013): FaceTime HD Camera may not work with some applications
Some applications not developed by Apple may not recognize the built-in FaceTime HD Camera or may display a black screen on MacBook Air (Mid 2013) computers. This may also occur with Final Cut Pro X v10.0.8.
Update any affected application to the latest version. Contact the developer for assistance with applications not developed by Apple.
As a work around for Final Cut Pro X or other OS X video applications, you can use QuickTime Player's New Movie Recording menu item. Use this to capture video from the built-in camera and then import the clip to the application.