Can you create a new block, like a bitcoin block, that ties in with economy? Just an idea for a plugin, sorry not a map!
Hmm. I personally couldn't, but that is GENIUS! I love it! Get a Bukkit plugin-maker to script that.
A tag on idea... When the bitcoin is mined, it releases a security key, allowing the map owner to reward players with real bitcoins. If anyone gets this working, let me know!
Or alternatively, you could store a real bitcoin wallet in a block.