"So George Soros and Warren Buffett say gold is the ultimate bubble?"
Soros has been happily investing in gold for a while, and still does (so far as I know).
Soros said gold was the ultimate asset bubble, but he ALSO said that it was rational to invest in a bubble at its start.
http://www.bloomberg.com/news/2010-08-30/gold-rallying-to-1-500-for-analysts-as-soros-s-bubble-inflates.html