>>Gold supply could be considered tighter than most other commodities because of natural scarcity. However, practically all gold is cumulated, i.e. it is always available for sale at right price. It makes gold price more dependent on macroecomic factors (euro/dollar rate, inflation, GDP comparative growth, etc) than on supply/demand factor more relevant for other commodities.
>>Silver supply currently exceeds demand and this situation will continue for few years because of significant supply expansion. Silver demand is also expanding quickly due to new technological uses (solar energy s one of them) but so far cannot catch up.
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>I guess the removal of need for silver in photography - with everything going digital - has probably reduced the demand for silver. Though the amount of silver in the emulsion was never significant; a decent photo lab may have extracted it from used-up fixer, but the value of it wouldn't exceed the cost of the chemicals in the process. In big numbers, however, it must have meant something. But I wonder how and when was this switch from silver to digital felt on the market.

It is an old and ongoing factor. In older times 60% of silver was used in photography, now it is about 20%, and this share shrinks by 10% a year. However, new silver demand coming from electronics more than compensate for that. As I already mentioned solay energy installations (photovoltaics) are big potential market for silver.