I like the feature, to be clear. I just think it's horribly executed, and the education side has been even worse.

The problem is that they took something. Then they changed it, giving it multiple nearly-invisible modes it can be in, which changes from application to application (not all have a 'revert' option, even for versioned files). Then they didn't tell anyone.

For instance. I just cropped this file. How do I know the original still exists? http://cl.ly/image/2L2X0x042W0N

Here, I opened it in another application. Are there multiple versions? http://cl.ly/image/3Y1m3C2r1r2f

What about in the File menu? http://cl.ly/image/0F2o2H2i3Z2f

Finder? http://cl.ly/image/1C0S3z3Z0q30 or http://cl.ly/image/463p0O1I3q1C or http://cl.ly/image/1F191E3b3U1W ?

(edit) Oh, cool - there's a "Versions" column. Maybe that has it: http://cl.ly/image/2703273U3z2U

This is bad.

Always assume that every change you make is saved automatically, much like cutting down a physical photo.

If you still want the original photo, and another cut down version, you would use a photo copier to Duplicate the original, then cut the copy.

"Always assume that every change you make is saved automatically" - You must have had a hard time dealing with computers until now :)

The real-world analogy makes sense, but it doesn't fit with how things have behaved. This is likely an improvement overall, but it's creating a period of upheaval and damage to people's property where better notification of the changes would make it a non-issue.

To modify and drag out the analogy to absurdity: say you previously made cropped photos by photocopying with a white rectangle mask revealing only the portions you wanted duplicated. Now, suddenly, you find that photocopying with the mask in place crops your original photo, without telling you. Nested a layer deep in the photocopier's menu is an option to undo the changes to your original.

I claim this is fine... if and only if the photocopier tells you of this before or immediately after, so you know to copy the whole thing first, and then cut, or use the 'revert' option. In a couple years that may be unnecessary, but not right now.

When I spent hours in a wet darkroom, I used a masking frame and the enlarger head height adjustment to crop a print, having previously marked up a work print. The negative was untouched.

The larger point I am making is that by referring to 'real' objects, we will return to a point where there is no system wide consistency any more. Case in point: editing audio tape or cine film did destroy the edited version, which is why we used prints/copy tapes.

Disclaimer: I don't use Mac OS. I do look to Apple for UI design however.

iOS doesn't show "EDITED" next to the filename in any window title bars either. I would think most people seeing "filename.txt -- edited" in a window title bar (such as in osx 10.8 TextEdit) would assume the file has not yet been saved.