I miswrote: All this is more wasteful than gold mining.
Ha ha! That was supposed to read “no more wasteful than gold mining.”
To put my answer to Michael Froomkin another way, bit gold is based on an unforgeable auditing log, a chain of puzzles and solutions each of which is timestamped. The entire value chain from puzzle to solution, and all transfers of title, are available for all bit gold and can be audited by anybody at any time.