Is it normal Mountain Lion behaviour to save changes in Preview without asking? I just opened an image in Preview, selected a rectangle, hit delete and then quit Preview. Now I have a grey rectangle missing from the middle of my image but at no point did I get a chance to say whether or not I wanted to save my changes.

Is this normal?

(I made the edit just to have a quick play with Preview, see what it can do. Needless to say I'm not impressed)
Yeah, Preview has supported auto-save since 10.7.

The general preference pane has an option to ask to keep changes when closing documents. It can also be applied to individual applications:

defaults write com.apple.Preview NSCloseAlwaysConfirmsChanges -bool true


You can also disable auto-save and Versions completely:

defaults write com.apple.Preview ApplePersistence -bool false