Technology that induces fear
One core HCI principle is to never make users feel out of control, since that easily induces frustration, uncertainty, or even fear in people. Modern Subway gates is one example of technology that fails on that particular point. The old ones were mechanical and were fully controlled by the person who passed through them. Now, the gates are electronic and as a user, you have absolutely no control of when and how they will open and close. It is like one of those old medieval assault courses where you have to pass swinging swords and other lethal obstacles.
I say: Let’s get them mechanical gates back!