It's a system that's based on trust, but the auto-update that is active in WordPress has saved millions of sites of getting hacked in the last few weeks: https://ma.ttias.be/in-defence-of-wordpress/

As soon as something major breaks by those auto-updates, the trust is over and a lot of users will disable it. That would be a shame indeed, because besides a couple of WSOD's some users may experience, it's an extremely powerful feature.