[JCB_K]

There is a downvote button, it's just visible after a certain karma threshold, which moves up at the same rate as "karma inflation".

[sp332]

There's no downvote button on stories. That encourages people to leave negative comments, because they can't express their "negativity" by downvoting.

[chris_gogreen]

Nice, I better work on my Karma. Thank You!