Also, that "Cancel" button is pretty ambiguous. I'd think "Eject Disk Image" and "Proceed Anyway" would be better options.
If Apple is consistent with their past behaviour and their uncanny understanding of user psychology, setting the "Allow all unsigned programs to execute" option in System Preferences won't add a "Proceed Anyway" button - it'll just suppress this dialog altogether.
So there will be no way to bypass this in a per-app basis without changing the system preferences for all applications? You either completely disallow unsigned applications, or you always allow them?
I'm not sure that's the best approach, but I'm not sure it isn't, either. :)
That this isn't achievable directly from the standard dialog is probably a good idea to avoid training Joe Average User to become blind to the warnings.
> That this isn't achievable directly from the standard dialog is probably a good idea to avoid training Joe Average User to become blind to the warnings.
Yes, this is a very good point.
I feel like there's a (probably smaller, but still not insignificant) middle ground of people who generally know what they're doing, but would still like the extra layer of protection, for whom the per-app exceptions would be handy. Having it not the default, though, is probably a good thing.
Well, that's effectively what the default is, where the "middle-ground" people will know to go into the contextual menu (or if you're feeling particularly keen, to disable the quarantine bit on the DMG from the command line, which is what triggers the signing check in the first place).