BOSTON (TheStreet) -- Commodities cratered last week, with silver posting its biggest decline since 1975 and oil recording its largest drop in three years, sending a chill through the markets as the hottest, and best-performing, investments turned cold overnight. Increases in Comex margin requirements decimated bets on silver, which plunged 27% in a week, and gold slid for three days, the worst decrease in a year. Individual investors, who have been playing the commodities markets through exchange traded funds, have been burned.