This is a rather graphic demonstration of the risk that investors run when they are shorting. When you go long you can lose up to 100% of what you have invested, but when you go short the amount you can lose is basically unlimited (because the shares may keep on rising). It demonstrates that one is not the mirror of the other, in addition to showing that shorters are not necessarily better informed (or more rational) than long-only investors (as implied by the argument that shorting can prevent the emergence of bubbles).
UPDATE: Nick says I'm talking ballax (see comments). I might be! A bit.