I feel that every time a new image is posted, the image is flooded with captions and everyone is trying to get the top caption and steal all the points for themselves, by whatever means. If this means down-voting all other comments that get sent to the bottom. In the aim of equality and genuinely trying to make Imgur even better, maybe it would be an idea to implement a time limit before a caption can be downvoted?
Therefore insulting or rude captions will only remain for a short time (say, ten minutes but the time can get less as Imgur increases in popularity), people who try to ruin Imgur's fair captions system don't get the one-up on everyone else, and people can still up-vote whatever captions they feel re the funniest/wittiest. Just an idea, probably worth a trial run and some feedback on your blog first.
Other than that. Imgur is my #1 website :) All we need now is that Imguraffe ;)