You say that, but when consoles get compromised, they get compromised on a massive scale. The continuing (and for whatever reason swept under the rug) large scale theft/scamming of people playing Fifa and the massive PSN security failure of a year or two ago is proof of that.Consoles are a whole lot more secure than regular PC's, at least they have in the past. We'll see with this one, but the closed nature of them makes it a whole lot harder.
I seriously doubt they would turn the camera on without you answering the call. I could see the friends video feed popping up saying you have an incoming call, but it won't auto answer for you.
Microsoft isn't immune. Look how easily Hotmail gets compromised.