Luke, it is rather unfortunate that you offered a problem (How to incentivize people) and a single potential solution (use karma) in the same post, committing what seems to be a rather basic violation of rationality, something one would hardly expect from an expert in the matter.
Now, as you can see from the comments, nearly everyone has concentrated on discussing your solution, as opposed to offering their own, and the utility of your post has been greatly diminished as a result.
Then again, maybe it was your intention all along, in which case I would appreciate your thinking on the matter. (For example, maybe there was some other post where plenty of options were discussed and karma use was agreed to be the way to proceed.)
Currently, LWers get +1 karma for a comment upvote, and +10 karma for a main post upvote. But clearly, there are other valuable things LWers could do for the community besides writing comments and posts. Writing isn't everyone's forte. Why not award karma for doing productive non-writing things? It's probably not optimal that karma and the community status that comes with it are awarded only for the thing that myself and a few other people are good at. For example, I really wish LW could award karma to programmers for improving LW.
The challenge is doing it fairly, in a way that doesn't alienate too many people. But there might be a workable way to do this, so let's explore.
Perhaps tasks could be assigned karma award amounts by LW editors (Nesov, Eliezer, Louie, etc.), or even just one person who is appointed as the Karma Genie.
Examples: