Incidentally, a couple days ago I spoke to someone wearing sunglasses. I did not find myself wondering if he was zoning out even though I couldn't see his eyes because there were other indicators that he was engaged. I did not check to see if the iPhone in his pocket was recording, nor did I really focus on his button up shirt to see if there was a tiny camera recording me.
In an essentially pre-Glass world all the technology needed to zone out in social situations while surreptitiously recording audio and video already exists and is accessible, yet I've never really worried about it. I strongly suspect this is a made-up problem. There may be many issues with Glass, but my hunch is this won't be one of them.