I'd read the 'by default' as it being turned on system-wide and up to the user to override on a per case basis. Of course Apple's ideal model is that they want

I'd read the 'by default' as it being turned on system-wide and up to the user to override on a per case basis. Of course Apple's ideal model is that they want everything going through them. They're going to enable it 'by default' and if customers don't scream too much, they'll likely make it mandatory a release or two later.