I guess since the NSA does it, Facebook wants to as well.  They've filed for a patent to secretly watch users through their webcam. https://www.independent.co.uk/life-style/gadgets-and-tech/news/facebook-plans-to-watch-users-through-webcams-spy-patent-application-social-media-a7779711.html

Sure, they say they'll never use the technology.

I don't think my webcam can see through electrical tape...