In my short time using evernote - this has been my workflow to avoid data loss:
only use the iphone or web version as "read only". If I want to edit or add-to a note - I simply create a new note and append it to the note I wanted to add it to later, while using the desktop version (which has undo). the thought of losing information is frightening to me - but if I lose a quick todo note while using the iphone app or web version...it's not as big of a deal.