I'm a month behind reading a fascinating post and discussion about the possibility of editors receiving a small commission on the sales of books they edit at Pimp My Novel.
In my limited experience, my editors have been involved in sales to a small extent. I know one of them talked about one of my books at a conference she attended, which is certainly like marketing, and I believe that they both had to "sell" the publishing house on my books to get them published at all. So there may very well be a sales aspect to editing. I don't know if a commission would make good editors do even better editing, but perhaps it would encourage them to work harder on that sales portion of their work life.
Of course, also in my own very personal experience, there are only so many hours in a life. Anything you choose to do means you are forced to choose not to do something else. If editors start working sales a little harder, maybe that will mean they have to let up on the editing. And books do need to be edited no matter what anyone tells you to the contrary.
I also wonder if editors working on commission would be less willing to take chances on what they acquire. We've been buried in vampire books and paranormal this and that these last couple of years, presumably because of a belief that what made money for one publishing house will make money for another. Imagine how much worse it could have been if the people doing the acquiring had reason to believe that their own income would go up if they could only acquire the same kind of money maker that worked for somebody last season.
But I'm not making any serious predictions here. The consequences of any action often come as a total surprise.