I wish there was a reputable market for shorting bitcoins. It'd be nice to earn some interest on my long position while providing the naysayers a chance to bet against it. It'd also help with the volatility.
I would be very happy if there was bitcoin shorting. It would become less volatile so we could actually use it for stuff without guessing if we are getting a 10% discount or 10% haircut compared to the next day. If there were a reputable market that did bitcoin futures I would take a very long position in bitcoin because that would make it useful for commerce and therefore incredibly valuable.
It would help if, for example, you needed to have BTC on hand for your business but you wanted to hedge away your exposure to the exchange rate with the USD.