Due to the ongoing turmoil in the financial markets a short-selling ban is being considered (again, one has to say, but this time in Europe):
Aside from the point that this seems to serve purely political reasons (since it is pretty clear that short-selling is not the culprit, quite the opposite as a ban will most probably lead to even more market volatility) I have a different question:
Concerning the experience with past bans: How was the derivatives markets affected esp. futures and options? There will be studies out there, I hope. This is also interesting with respect to the question how important hedging with linear instruments really is for market makers.