I should point out that there is no comparable limit on upvoting, AFAIK, so it may be possible to make 10 accounts, post 1 comment on each, get +9 on each (by having the other 9 accounts upvote the 10th account's 1 comment), and now you have 10 9 4 = 360 total downvotes available (10 accounts with +9 karma and 4 downvotes for each karma point).
True. And that is per comment, so if each puppet makes ten comments before you start the circle jerk you can make ten times as many downvotes as that, assuming that you click quickly enough. But then there are also people who downvote comments that they think have too good scores, so unless your comments actually are good you will have to make and multi-upvote more and more comments to keep constant karma.
If it's worth saying, but not worth its own post, even in Discussion, it goes here.