Remember too,

When you buy stock, your losses are  limited (it can only go to zero) 
while your gains are unlimited (you might be able to sell it for any 
price later).

When you sell stock short (sell shares you haven't bought yet), your 
gains are limited (it can only go to zero) while your losses are 
unlimited (if it rises, you're really out of luck).

Because potential losses are infinite, "shorting" might not be suitable 
for all investors.

\\/