I used to invest in silver back when the price was ~$27/OzT and rising. It got to around $40 and I was about to sell (I was waiting for it to hit $45) and then the Gov't stepped in and made a ruling that regulated the price of silver. I think they flooded the market with bullion. It dropped to <$25 in one night. I wound up losing money. I waited months for a recovery but it never did, so I sold off my bullion at as little of a loss as I could and swore off precious metal investments.
So far, Gold, Platinum, and others have no shared the same fate that Silver did, but fact is; there's nothing at all stopping the government from doing the same thing to them. As long as that is the case, there's no reason to risk your money. Gold is still a viable investment it seems as there is limited growth due to very low industrial demand; the very thing that made silver attractive (aside from the low buy in price). But should a rapidly expanding demand for it rise up, there's little to say the same thing won't occur. The government does not want its currency to become second to a commodity trade, period.