Not to invest, but to preserve your wealth says Ron Paul:
Buying gold and holding it is somewhat analogous to converting one’s savings into one hundred dollar bills and hiding them under the mattress – yet not exactly the same. Both gold and dollars are considered money, and holding money does not qualify as an investment. There’s a big difference between the two however, since by holding paper money one loses purchasing power. The purchasing power of commodity money, i.e. gold, however, goes up if the government devalues the circulating fiat currency.
Holding gold is protection or insurance against government’s proclivity to debase its currency. The purchasing power of gold goes up not because it’s a so-called good investment; it goes up in value only because the paper currency goes down in value. In our current situation, that means the dollar.