Wave Systems Corp. (fka WAVXQ)

[player1234]

Actually, your math is slightly wrong. It's a mistake most people who don't short stocks often make.

If you short it at $1 and it goes to 0.90 where you buy it back, you have made 11%, not 10%. (Not much of a difference in this case)

Bought it at 0.90, sold it at $1, $0.10 profit.
0.10/0.90 = 11%

Your other example is also off:

If you short it at $1.20 and it goes to 0.90 where you buy it back, you have made 33%.

Bought it at 0.90, sold it at $1.20, $0.30 profit.
0.30/0.90 = 33%


The fact that you sold it before you bought it is immaterial to the percentage gain.