There’s a good article floating around on Gawker (rare, I know) about the site Silk Road, an online black market for narcotics set up to function like Amazon or eBay. The fascinating part: it doesn’t accept credit cards or Paypal, only Bitcoins - one of which is worth about $8.67, though the exchange rate fluctuates wildly every day:

Bitcoins have been called a “crypto-currency,” the online equivalent of a brown paper bag of cash. Bitcoins are a peer-to-peer currency, not issued by banks or governments, but created and regulated by a network of other bitcoin holders’ computers. (The name “Bitcoin” is derived from the pioneering file-sharing technology Bittorrent.) They are purportedly untraceable and have been championed by cyberpunks, libertarians and anarchists who dream of a distributed digital economy outside the law, one where money flows across borders as free as bits.

article here