The big debate of the benefits of adding CCF (collateralized commodities futures) funds to a portfolio continues on the Diehards forum (48981). As for myself, I had previously bought PCRIX as part of my Precious Metal / Commodity asset class allocation but decided to eliminate it due to difficulties in re-balancing and performing DCA (PCRIX is a transaction-fee fund at VBS). I replaced it with VGPMX instead.
The new ETF DBC sounds interesting but I would defer any consideration until the expense ratio is lowered to at least below 0.8%.