I think it is only normal that 50% is down and 50% is up.
Why? Do you think that posts are completely random? Or do you think that posts should be graded on the curve? And your 50% figures leave no room for neutrality. I think it is "only normal" to expect people to post when they believe they have something worth posting -- that is, positive-worthy posts should outweigh negative-worthy ones by simple self-censorship. It's only when an error (or difference) in judgment comes out that a downvote-worthy post appears.
People obviously have differing ideas about what merits each kind of voting response (or non-response). My view: Many posts are fairly straightforward and obvious, or mildly flawed. Those merit no response. A fair number of posts demonstrate elegance and/or insight that merit an upvote. A very few are so incoherent or misleading that they should never have been posted. Those merit downvotes.
I have noticed more downvotes of my posts, lately, too. In fact, they seem to come as a burst of three. They have been unexplained, and from my POV, inexplicable. I'm not concerned about XP, but I am concerned about posting things that are worthwhile, and getting feedback from others that could help me make my futures posts moreso. The downvotes I've received have been useless in that regard. The only bit of information I can glean from them is that there are some jackasses around.
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