I'm out!, page-9

A short squeeze works in two ways. Those that cant increase their  margin have to cover when the SP rises which increases the price. The other factor is large amount of sellers. When shares are put into market they are recalled from brokers. The brokers then force shorts to cover positions because the owner of the shares wants them back. So not always a good thing if there are many buyers and few sellers. Shares aren't recalled and allows shorts to hold their positions for many months waiting for a downturn.