Shorts have a place... I don't short, it's problematic for the following reasons:
-it's an asymmetric bet, to the short's disadvantage
-it bets against the success of an enterprise pursuing a profitable benefit to society
-it bets against a discrete community of common stakeholders, with non-zero lobbying power
-on a sufficiently long time scale, a given equity's value tends to increase
-it's a contrarian investment thesis, which only generates value after enough people acknowledge its validity (i.e. enough people change their minds about what's contrarian), always a dicey proposition
...the more the above factors fail to apply, the more possible a short might succeed. Protective puts are about my limit.