@Aron -
I'm not saying, no one I've seen, are saying it can't break. It can, but it still unlikely and a very few sites affected.

I this case, automatic update would have been cancelled, because the problem some got was spotted within the delay time. How many hours, days or weeks (?) should pass after a security release before automatic updates are pushed? That's the question.

The point is that this quite rare cases are outweighed hundreds of times with all the almost abandoned, the static sites, that may be in jeopardy if not ever updated.

To me such automatic updates are as obvious as it is mandatory for a plane to be retrofitted or repaired when a similar plane has had a serious incident, and the cause of that is the plane's technical state. You don't wait until the captain or the airline feels the plane needs to be repaired. And, of course, the repair may introduce unforeseen problems.

There are a lot of software having automatic updates, and this is great success in combating publicly known vulnerabilities being exploited.We are on the internet, there is not only the cause of the sites owner, but the global, online public.

It's exactly "the mainstream" that will benefit from this. Hacked sites, he spread of malware and fraud through such sites is an alerted disaster. WordPress not doing this, at least trying it's best for now, would be a todays "McDonnel Douglas" of 1973 (DC10 scandal).