Bitcoin fell below $100 on major exchange Mt. Gox early Friday, dropping under a key psychological threshold. Traders pushed the digital currency as low as $91.50, far below its price at around $537 on two other exchanges tracked by CoinDesk.com. The price on Mt. Gox later recovered to around $100, but it remains the cheapest exchange in the world to buy Bitcoin. The price drop followed another update about a technical issue that prompted it to suspend Bitcoin withdrawals to outside addresses two weeks ago.