You probably already know that I do not believe that oil will reach $300 or $400 a baril, nor do I believe that gold will reach a five figure price per ounce or silver to reach $150 or $300 like many über-bull believes. I actually believe that we'll have a major collapse in risky asset classes, but time will tell.
In anyway, I wanted to make a few arguments against those forecasts because greed seems to disable some of the thinking areas of the brains of these otherwise clever people (most of them, at least).
First, demand is not 100% inelastic as they seem to believe. A baril at $150 destroyed a lot of consumption in 2008. And believe me, a lot of people will stop taking their cars and start carpooling, working from home, and taking public transports if the price of oil goes back to $150, so that even $200 seems unlikely.
Second of all, imagine that oil would actually reach $300 and that other soft/grain commodities such as wheat and pork bellies would skyrocket. Do you believe that everything would be rosy? The most probable outcome of such a move would be major civil unrest all around the world, and probably even war between countries who do not have oil and the producers. Believe me, I'm about as sure as possible that the US would start invading other countries in the name of war on terror and that China would also start annexing countries for their oil.
The $300/baril of oil scenario remains very unlikely, but be careful what you wish for nonetheless.