Stock price is the price of the last share sold, not every share. If someone tried to raid Zynga for its cash, buying up all the shares, they would buy all the shares offered at $2.35, then all the shares offered at $2.45, ... until they end up paying $3 or $5 or $100 for the 50% ownership they need to take over the company and shut it down. The total cost of the company would be more than (last share sale price) * (# of shares)