Robert Rohde wrote:
As I recall, someone did an analysis and reported that people click on "edit" more than twice as often as they actually save an edit.
It might be useful to save every "preview" at the server as a "personal draft", a new version of the the page [[Special:Draft]], visible only to that user and that only remembers the 100 last versions of whatever that user previewed (or diffed) during edit.
The performance issue would be small, since the server already has to handle traffic in and out for each preview.
This would be a low-tech approach to auto-saving, one that involves the user more and doesn't use any magic background Javascript.