Glad you brought that up, the fees and margin rates posted by the brokerages are meaningless, particularly for folks experienced and sophisticated enough to be shorting pinkies. As I recently shopped brokers, I was offered $4.95/per trade with Schwab ($9,95/per trade advertised on its website), $4.95/per trade with MB Trading ($8.95/per trade advertised on its website) and $5.95/per trade on Realfasttrader.com ($9.95/per trade advertised on its website). Then I told Ameritrade I was going to switch and they matched those offers and also reduced my margin rates (but they still wouldn't let me short pinkies or buy PNMS). And I'm no big fish, I just make a lot of trades so they negotiated with me. So anyone that says its prohibitively expensive to short because of the advertised commission fees and rates, no, those can be negotiated.
BTW, I opened an MB Trading account as a backup. And on Friday I tried to buy PNMS and they had restricted all online trades! I ended up having to call in. I screamed at them, "but that's the only reason I opened up a freakin account with you people!" LMAO. At least I got me some.