It's stupid to have a short position on a stock that has gone up in value 40-50% some days. Sure it has come back down an equal measure other days but you are gambling
1) On the day that you have to deliver the shares the value didn't go up
2) Good news causes the price to spike, either temporarily or permanently.

What if I decided to short 100,000 shares of Mesa today. At an average price of 20 cents thats 20 grand. I borrow 100k of Mesa stock from someone. I have 3 days to deliver the 100,000 shares at a price of 20 cents. If my guess is right and the price drops to 10 cents then I would get 10,000$, minus any margin fees or comissions. If they declare BK and the stock drops to zero then I made the entire sum of 20 grand.

HOWEVER

If I am wrong there is NO LIMIT to how much money I can lose. If the price doubles I have to buy 100,000 shares at 40 cents -- I lose 20,000$. If there is a news flash that Mesa picked up new flying and the price goes to a dollar, which isn't an unreasonable price point for it then I lose _$80,000_.

This is why I never understood short sales. With most things the bigger the risk the bigger the reward, but with this the bigger the risk the smaller the reward. At least if you just buy Mesa stock the only thing you'll potentially lose is the money you put in -- if a short sale goes bad for you you'll lose all that and then more.

Right now Mesa has about a 1.5% short interest which is half of what Delta's percentage is, which shows you that people, smart people, don't short such voliatile stocks.