On the main subs, I think it is that there has been a down tick in the average user age. Being on the site and not being logged into my account feels quite a bit like visiting my 14 year old little brother facebook page. Just kind of base-line, 14 year old funny.

My point being, I think a percentage of the trolling may come from that demographic. It's not rare to run across account that literally was set up just to hurl insults and racism. I just imagine that there are a group of 14 year olds sitting on the other side which boast to each other about how much negative Karma their 'troll' accounts have.

In other areas, I think it's that some people just take karma far too seriously. I used to spend a lot of time in the language specific learnprogramming subreddits. It seemed like a nice way to help the 'community,' without having to do the race to the answer game that you do on stackoverflow.

I learned that some of the most unbelievably childish people hang out in the language specific threads so they can play 'expert.' I ran into a couple of users that would downvote every answer in the thread that wasn't theirs. I sent one a message about reddiquette and that fact that he's really being a bit of a dick in our small community, but his response was to downvote all of my posts, and say that all other answers were wrong but his (they weren't).

Needless to say, it seemed a waste of effort to continue to post if everything was just going to be buried thanks to some guy's e-ego.