It's very hard to short stocks. Most high flyers will eventually collapse. The problem is that you can't tell the difference between the bubbles and the actual

It's very hard to short stocks. Most high flyers will eventually collapse. The problem is that you can't tell the difference between the bubbles and the actual winners. You don't have to cover your shorts unless you breach a limit that the brokerage has set. That limit is based on how much liquidity you have. I suspect the majority of the shorts that can continue to hold their position are still shorting hoping to get out at a better price.