That's equivalent to saying that buying a stock doesn't move the price up because you'll have to sell it eventually. A lot of people in long positions means a

That's equivalent to saying that buying a stock doesn't move the price up because you'll have to sell it eventually. A lot of people in long positions means a lot of buys that haven't been re-sold. A lot of people in short positions means a lot of sells that haven't been re-bought.