Interesting article on using the "taxi driver indicator" to judge if something is a bubble. I also find it interesting that, as a percent of investment portfolios, gold is still less than one percent!
http://wallstcheatsheet.com/investing/are-taxi-drivers-buying-gold-or-apple.html/
http://wallstcheatsheet.com/investing/are-taxi-drivers-buying-gold-or-apple.html/