Mac Performance Guide writes about data loss with OS X Mountain Lion and Save As. The Save As command was effectively removed from Lion, with Apple clearly wanting to end people’s reliance on saving at all, instead letting the OS deal with such things. In order to facilitate making copies of files (which many users had been trained to do via Save As), Apple provided a Duplicate option to clone an open document.
From what I can tell, Apple’s brave new way went down like a spoonful of piss. There was a lot of bitching and whining about Apple being stupid idiots for changing the way you deal with files. Personally, I liked the new workflow: I so often accidentally overwrite boilerplates, but the Duplicate option also enables you to revert the file you’re cloning from, which was for me a little slice of bliss.
Still, Apple relented and brought back Save As in ‘hidden’ form to OS X Mountain Lion (it’s only visible upon holding Option when you’re in the File menu). But instead of just saving a copy of the current document with a new name, it also overwrites the original with the same changes. Either this is a bug or Apple really has it in for anyone who doesn’t like its new ways of doing things.