Inspired by this article:http://bitcoinweekly.com/articles/anonymous-money-needs-an-anonymous-exchange
We need to start Ripple site in i2p network. (since the owner is unknown - it may be centralized)
Local (sity-wide) bitcoin exchanges can join that site.
Exchanges can trust each other on the basis of length of operation, popularity and so on.
Each local exchange should operate independently and have it's own website,
which explains how to exchange local money (different fiat currencies in different countries) to bitcoins.
In most countries it is legal to sell bitcoins for money, but illegal to cash out.
Cash out can be done by selling locations of treasures (yes, it is Dead drop
Site sells coordinates of location for bitcoins, visitor goes to location and obtains cash.
This way of cash out gives anonymity to exchanger,
if he visit locations only once and hide his footprints after that.