Click the little radioactive symbol next to the main karma link and this will apply negative karma. It won't reduce the good karma but will have a count of its own instead. Bad karma is anonymous - it won't generate a Smarty alert. Also, you can't give both good and bad karma to the same post.

We could sell special powers or features. The pluses situation is a bit out of control with the betting TBH, we should probably have a stake limit.