I've had two incidents in the past few days where I moved forward and back in my browser to check some info, then edited my post. Unfortunately I edited the original posting form rather than the edit form, and made duplicate posts. Now I know I have only myself to blame for this, but I thought I would recommend a fix we did at one place I worked:
Every time a node-creating form was loaded (or in our case, anything that would cost money), the form carried a hidden field with a value set at the load time. When the form was processed, this field was checked against a list of recently used values. If it matched, it meant that the form had already been posted, and the user was bounced to a preview screen and warned. If it didn't match, the form was posted, and the number was marked as "used" for a period of time. This doesn't stop EVERY occurance (one could come back to the browser after the expiration time and resubmit the form), but it helps.