I tried to short RIMM yesterday, but IB wouldn't let me. I got some cryptic message saying that this share couldn't be shorted. Is this because the share was falling so rapidly that there were no shares to lend me, or are some stocks unshortable?
http://www.interactivebrokers.com/html/tradingInfo/shortableStocks.html Click on US Shortable Stocks. Type in RIMM - none to borrow.