OK, here is a fix for both situations, mistakes and after viewing history clearance... and now that I think about it, may even help with another problem on this site.
Have a big prominent button on the main page, that, when pressed, immediately cancels the stream of the show, whatever it was, and returns the credit to the viewer. Make it so you have to hit the "eject" button before say, five minutes of the show has run. THAT should give you time to either A: discover you fumble fingered the mouse, B: realize you've seen this one before, and C: Realize you are having too bad of a connection to try to watching now and pull the plug on it, to wait for a different day or time to watch.
I don't know all of the technical aspects to it, but I imagine that it would be fairly simple to cause a pressing of this eject button to clear the download queue... and maybe have a script that, say at midnight, double checked to ensure you didn't click the same episode again that day, and if so... adds the credits at the end of the day. So long as you didn't watch it all the way through on the same day, it would seem, to me that you could kill a couple of birds with one stone on this.
Good idea?