An interesting point on money (and on the money), from NYT's article 'In Code We Trust':
There is a common perception that economists believe money drives human behavior. In fact, it’s almost precisely the opposite. Most modern economics is predicated on an idea first espoused by David Hume in his 1752 essay, “Of Money,” that currency, gold, bank slips, checks and so on are beside the point. What actually matters is what we make and do and feel and want. Money is just an imperfect tool to add it all up, to assign value to our fundamental human desires. We need money only because it, unlike passion, can be stored and traded and counted.
What's amusing is that everyone uses money on a daily basis, and yet very few people actually think about why it exists. Money itself can be whatever people want it to be, so long as there is mutual agreement on what the currency ought to be. It might even be a drawing of a spider. Remember that old internet story?