&gt;It can be solved by an exchange that makes trades every second or on some time interval that is minuscule to a person but enormous to a computer.<p>I do not see how that will solve the problem. Suppose firm A and firm B both want to buy stock X at prize Z. There is only enough X at prize Z for one of those firms. Both firms send their trade orders withing milliseconds of each other. In your time interval scheme, which firm gets to buy the stock?