It seems I made my comment before I saw your edit, that you were writing about only advertising and targeting. I'm not sure what your definition of consent is,

It seems I made my comment before I saw your edit, that you were writing about only advertising and targeting. I'm not sure what your definition of consent is, regarding video streaming on the web, but it seems to me that every implementation of the getUserMedia API on modern browsers asks the user for permission to access the device. So yes, anyone surreptitiously gaining access to your camera or mic feed through the browser would get into heaps of trouble and invite bad press, especially if they were able to find a way around the consent dialog.