Make a bunch of paper wallet for Bitcoin. 0.05 BTC, 0.1, 1, etc, like cash. Now go to a club, get drunk and use them as a medium of exchange for drinks and whatever else you want to buy under cover of darkness, where dozens of other people are doing the same, some with paper wallets you have paid them, some with standard denomination wallets of their own. Make sure the wallets are passed around lots of times.

The morning after, see if you can figure out who owns all the Bitcoins now, and what they've bought with them.

It's a bit like that, only more complicated, and the club is really a big p2p network that does things that shouldn't be allowed under the normal rules of the universe.