Well. It could be true for Google CEO, and many others. Technically, there are too many bad things that can happen. Laws are what that's preventing those.
My computer can phone home with my every keystroke or technically it's possible for a modern air conditioning system to release its refrigerant gas into the room with certain key combination on its remote. But until those are proven to happen, it's just a conspiracy.
In short, there are so many bad things that can happen, doesn't actually mean that will happen. At least - for many cases - that's better way to think, so that we don't have to live a fearful life. And in the cases we can, be in the safe side, like not using Facebook, using completely free software OS, putting a tape on camera, etc.
Edit: On a side note, it would be nice if HN team change http urls to https if the site supports it, and discourage links that requires javascript with no added value.