Interestingly, there is a new carabiner on the market whose locking mechanism is more like a button (http://www.rei.com/product/840193/black-diamond-magnetron-ro...): the difference being that the mechanism must be activated from both sides (via pinching the purple parts in the image), and has magnets forcing the carabiner into the "locked" state when not being held unlocked.
Also interesting is that the waist tether is adjustable. That could be a point of failure -- imagine floating off the end of your tether. Although I can't tell whether the waist tether is designed to attach astronauts to the spaceship, or just tools to astronauts. Howstuffworks.com implies it attaches astronauts to the spaceship (http://science.howstuffworks.com/spacewalk4.htm), but brighthub.com implies it's for tools (http://www.brighthub.com/science/space/articles/126178.aspx).