For one thing, I always try to provide a tested answer, but doing so means that someone frequently jumps in front of me, scoring the reputation. In many of these cases I can see that the answer provided might be conceptually correct, but wasn't actually tested, because there are typos in the code. Thus, it appears that the incentives are skewed away from providing the highest-quality answers.
I pretty much quit about two weeks ago. I spent time formulating an answer  that was entirely correct, so by the time I posted it there were three other answers there, but they relied on special cases rather than being generally correct. One person upvoted my answer, but almost immediately, someone else downvoted it. The only thing I can imagine is that one of the "competing" answerers wanted to ensure that his mostly-correct answer was listed above my completely correct one, so he could score points from readers that hadn't yet seen my reply that explained why special care was needed.
If my diligent work is going to be devalued like that, then I don't see the point in investing more time in it.
For example, I answered one question about some kind of 2d sorting issue - another answer popped up which was both incomplete (it only dealt with the 1d case, which was trivial) and incorrect (it claimed to run in linear time, but was blatantly using a nlogn sort). I felt that a downvote was the right thing to do - but that does rely on the honesty of the users, and it sounds like that's often lacking.
There's definitely a problem here and something needs to be done, but that's not the solution.
I wonder if something like displaying answers on newly asked questions, but locking voting for <x> minutes (where x=???), and total_answers < <y> wouldn't stop the answer sniping in its tracks and give people willing to put the proper amount of work into writing an answer an equal footing.
SO has proven that the community for some reason is more than willing to spend vast amounts of energy helping others in exchange for "karma", but from what I'm reading lately, they are somewhat in danger of letting the golden goose die (or, a lot of the golden gooses). It'll still be a great site, but it could be a lot better if they tightened some of these problems up. I think they might be focusing on other things now though.