Even though the vast majority of economics and business talking heads support the practice of shorting* as a mechanism of "price discovery," the SEC has gone and banned it, in part because of the bad press it has gotten in these recent financial stock fallouts.
It seems to me that we (the govt, investors) just don't want people betting against stability. It's a legal, fair option that's on the table, like "Don't Pass" on the craps table, but like "Don't Pass," it's usually precluded by etiquette, even if the odds are better in certain situations.
* In my opinion there's nothing nefarious about short selling, in principle, but in practice, I happen to believe short sellers must attempt to create rumors and spread false information to make stocks drop. It's just rational economic behavior. But it's hard to support a practice that thrives on panic. Short selling, to me, is like price gouging -- it's "fair" in the sense that's it's just reflecting supply and demand, but it feels dirty.