There's a ten-month-old widely-supported proposal on meta meant to address this, but it hasn't received any comment from the Stack Exchange Inc. folks. http://meta.stackoverflow.com/q/90620/134300
- rewarding with rep could convert answerers to closers
* answering produces useful stuff, closing is (often) just clerical
- over aggressive closing drives new users away
* blatant laziness shouldn't be rewarded, but subtle variations on a problem shouldn't be punished either
- some level of duplication is a good thing
* in a nutshell, people ask the same conceptual question in different ways, it's good to have all those ways around to help Googlers
We've also improved finding duplicates in the close dialog since that meta post (it's a hard problem, so it's not a perfect suggesting system), so it's hardly like we've done nothing.
Also, as written that feature request is unworkable. Incentivize closing over asking, madness. Even incentivizing over editing (+2 up to 1k rep) is harmful IMO. I suppose we could just decline that post, but what'll probably happen is it'll be status-completed when we've come up with a better solution (which will be documented in an answer).
^ Based on the most recent data dump, somewhere around a 15 - 20% of closed questions (which are about 3-4% of all new questions). That sounds about right, honestly. I'm sure some stuff is slipping through, and we could make it easier to maintain these rates; but it doesn't seem like a pandemic of duplicates.
Oops, forgot the disclaimer: Stack Exchange Inc. employee, etc. etc.