Of course, you can also opt out by only doing updates by FTP and never giving your user / pass to the wordpress software itself. Automated updates scare me greatly, in part because it means that there is a certain amount of access granted that I cannot easily control. It's almost inevitable at some point that a hacker will get access through this sort of method.

I should also say that until Wordpress has true control over the content of all updates, I wouldn't recommend it. From plugins that don't work to themes that either have issues, don't format correctly, or that are entirely different one version to another (byblos theme, example), automating updates in any manner is a huge risk. It may help some security issues, but on the other side, it risks causing errors or even making your sites unavailable or worse causing issues that Googlebot will toss you out for.