But then I also can't disagree with rookie's observation that central banks are reluctant to part with their gold because it's the most valuable thing they own.

You are viewing their decisions with 20/20 hindsight and the knowledge of a current price of gold over $1000/oz. They certainly didn't view it that way when gold was ~$300/oz. A 'barbarous relic', I believe it was referred to by more than one prominent economist.

Have you ever heard of the Brown Bottom?

"With many gold traders shorting, gold reached a low point of US$252.80 on 20 July.[8] The UK eventually sold about 395 tons of gold over 17 auctions from July 1999 to March 2002, at an average price of about US$275 per ounce, raising approximately US$3.5 billion."

I'm saying that the borrowers must have signed some sort of agreement to return the gold. It is difficult to conceptualize a situation in which it's okay with the Fed if the bars are never returned. That kind of reckless action could be labeled as treason.

Little is known about these agreements. Attempts by GATA and others to find out more about how much of the US Treasury gold was leased and swapped, and under what terms, have been rebuffed for reasons of national security. Attempts by Ron Paul to introduce bills to audit the gold at Fort Knox have not made it past the Congressional floor.

I think it is very likely that most or all of the gold suposedly held in Fort Knox has been leased out, never to return. Does that constitute treason? Is it treason for the Federal Reserve to implement the monetary policy of the US Treasury? Was it treasonous for Bush Sr. and Clinton to doctor economic statistics to downplay inflation, thus meddling with bond market yields in order to lower their borrowing costs?

If you look at the US Constituion, probably. But then so would be the creation of the Federal Reserve.