most people know very little about investment

but they can put all their money in Birkshire Hathaway for 20-30 years, probably still beat S&P 500 at the end. Can they do the same thing in GLD without hedge, without losing any sleep?      

Holding gold does not create any economic value.  You can not eat gold, or drink it, or drive it. It is a pure speculation, not an investment. The day gold ETF went to skyhigh, you would probably want to go out to get a bunker, lots of gun powder/bullets, dry food and water. Realizing the paper gain on your gold ETF is probably the least thing you need worry about.    

I do own low cost gold mutual fund, but less than 5% of my portfolio.  

Another loophole in your logic is, even though the gas price rised 81%, does the ratio of your total gas bill over your total income also rise 81%? The total consumption of gas have been declining steadliy for the past 10 years. The gas price doesn't matter that much as in the past, like 30-40 years ago. Furthermore, with the development of oil fractionation technology, I had a hard time understanding oil price can sustain the current level.  Have you noticed how cheap the natural gas price is now?