My guess is light volume and the way trades are made. I could put an offer in for a contract at $5 per ounce, and it will never be taken except in one occasion. I happen to be the only bid on the table AND someone coincidently places a sell at market (a market order). A market order goes to the highest current bidder. That makes a trade and there are a lot of people (spell that T-H-I-E-V-E-S) out there waiting for someone to make a mistake like that (the market order). I've been tempted but I never had the stomach to do that to anyone. Only a greenie would put a market order like that. In a normal or heavy market those bids just expire.
Constarnation, the things you find out on there there internet!! I think I'm going to find a way to have a standing buy at $5.00 placed and renewed every 10 minutes. I wonder what kind of fees are involved? If I can hook an order on paper, I just might be able to take physical possession...