Depending on what you're doing that you don't want "them" to see/hear, you could be right. I work mostly solo, and I'm not in the habit of verbally announcing everything I do, so personally I'm more concerned about the cam. But you're right: reliably disabling the mic would be a bitch on most modern machines (laptops, phones, tablets, and iMacs). Only machines with no built-in mic (e.g. desktop, Mac Mini, Raspberry Pi) would be inherently immune to this vulnerability.