Irrational Exuberance (IE as I abbreviate it) (credit to Alan Greenspan) will explain some of the "spikes" on the above chart. I am old enough to remember foolish buyers lining up for the opportunity to purchase gold and silver in the 80's and also actually waiting in line so my Las Vegas client could purchase an overpriced new builder home. The dotcom IE isn't on the chart but should be there, too. as another example of IE.
I would be fearful gold prices are a result of IE and may be overpriced.
Of course this is a simplified analysis but when the average Joe is lining up to buy something, Sell it Short!