It's interesting. I was just looking at a user account that had a gazillion post karma, but -10 comment karma. It also created a few subreddits. It's so obvious a content farmer.

People moved away from Digg because they implemented an algorithm to suggest news, and de-emphasised user submitted stories. Now, essentially the same thing is happening with reddit via these farmers. It's not as obvious and might not be sanctioned, but at the end of the day, a few select bots are also pushing content to the front.