Is there a way to disable or turn off iSight?
(re)moving
/System/Library/Extensions/IOUSBFamily.kext/Contents/PlugIns/AppleUSBVideoSupport.kext
should do it
Note: changings in folder System will be made at one’s own risk 
Great! Thanks.
A quarter-inch square of electrical tape will have the same result.
Although that’s prolly not the most aesthetically pleasing method.