It would distort markets. Besides, if I bought a load of gold when I thought the price was going up, then it would drive up the price at that point. When I came to sell in the future it would depress the price. Thus, I wouldn't make the killing I thought I would, would I?""Yeah, but futures contracts.""Same thing, dear boy.""Art, then.""If I bought Constable's Hay Wain direct from the artist it wouldn't have the same cachet as it does today. The absence of that piece from the market might mean that all of his work was devalued.""Yeah, but you could bring another piece back.""Ah, then the paint and canvas wouldn't age correctly. For older objets d'art, the carbon dating would show it was younger than it should be. Sorry, Kevin. You're not going to get rich by temporal smuggling or speculation.
Mark Speed, Doctor How and the Illegal Aliens
paradoxes, time-travel