It all started so well: a surprise drop in Treasury yields, expectations of accelerating economic recovery, and more than a dash of geopolitical turmoil.

Yes, 2014 was shaping up to be a good year for commodities. And indeed, the first half was more than acceptable. At 7.1%, the recently renamed Bloomberg Commodity Index (formerly the Dow Jones-UBS index) had its best six-month period since the latter half of 2010 and its best first half since that of 2008, when the supercycle's ascent seemed unstoppable.