In a Seeking Alpha piece, Dr. Duru points out that the put-call ratio on the SPDR Gold Shares Trust (GLD) keeps rising along with its price. That concurrency indicates bearishness, or skepticism regarding the rally, is moving up with GLD. That's not a sign of a momentum-driven bubble.
He supplements that result with some search-string research of his own. The string "gold bubble" in Google News shows an increase in the number of hits as the gold price rises. Search interest in both buying and selling gold has remained steady over the last several years. More recently, however, Web searches for "gold bubble" have slumped subsequent to late 2009.
It's an interesting analysis, and complements the put-call ratio data. I have to say that there is no all-out mania developing at this time.