click on chart to enlarge
London Stock Exchange statistics show that spreads of a popular physical gold ETF - the ETF Securities Physical Gold £ with the LSE ticker of PHGP - widened to 1.36% in the week between 10 April 2012 and 13 April 2012.
In the same week two other ETF Securities products also saw massive spikes in spreads. The most dramatic commodity ETF spread was ETFS Tin (PHSN) which saw its spread widen to 14.77% when it was (already quite wide) at 2.3% the week before.
Also (on the chart above) ETFS Physical Swiss Gold (SGBS) saw its spreads widen to 2.3% for the same period when they were usually between 0.25 and 0.57 in the other figures I looked at.