Just a couple of points here that I would like to comment on:

Northern Ireland also recently introduced bizzarre plastic bank notes. I had the opportunity to se one of these for the first time through the week, and I refuse to believe that it really is money. It just looks so wrong. Of course it doesn't help that the bank notes are printed in a profile format rather than landscape.

Also, in terms of making currency out of cinder blocks, I'm reminded of an essay entitled "The Roentgen Standard" by Larry Niven that proposed that money be made out of radioactive waste. As I recall the benefits were that pick-pockets would be easy to spot (either wearing lead gloves or with hands that glow in the dark), money would be less likely to sit around in bank vaults approaching critical mass, but would be spent as quickly as it was earnt, and counterfeiting would be impossible without a cyclotron. There was other stuff as well, but it's been a while since I read it.

Although, personally I prefer one of Heinlein's ideas on how to handle radioactive waste: Pile it all up in a desert with a fence all the way around and signs all over saying: "Warning: if you cross this fence you will die". If anyone crosses the fence, average IQ of the human race goes up a fraction of a point.

winter"Now there would be a Darwin Award"mute