What is a good analogy (which a layperson would understand) for the process of Bitcoin mining? I will be explaining Bitcoin to a non-technical group and I am hoping somebody can provide me with a very basic visual analogy of the crypto-currency mining process.

My half-baked idea, was to somehow describe the mining process as partaking in a complex word search. Hopefully getting my group to visualize a large pool table sized word search (block) and have them imagining searching for a 30 alphanumeric character identifier (wallet). Describing the blockchain as a city sized word-search on top of 21 million pool tables?


Is this a good analogy to use, or is there a better/more applicable one?
Using (and adding to) the best analogy, how can I explain the difference in mining with CPU/GPU/ASIC and why the ASIC hardware is the quickest?
I wrote a blog post called Bitcoin by Analogy that captures the best analogy I've seen for explaining Bitcoin:

The nation of Yap in the South Pacific uses a unique form of money called Rai stones, which are circular disks carved out of limestone, with a hole in the middle, that can be up to 12 feet in diameter and weigh up to 8,800 lbs!



Trading stones of this size is difficult: no one wants to cart around a 4 ton stone every time they make a purchase. As a result, the Yapese came up with a clever solution: they decided to determine ownership by verbal agreement. Whenever there was a trade, the parties involved would communicate to the rest of the tribe the amount of stone that had been exchanged. The stones wouldn't actually move from one house to another, but the knowledge of who owned what was memorized and handed down through oral history.

It turns out that this model of money is an excellent analogy for Bitcoin: the ownership of money is determined through collective memory (similar to Bitcoin's global ledger, known as the block chain), money is exchanged by telling everyone in the village about transactions (much like sending out messages in Bitcoin for each transfer), and new money enters the system through the time consuming and randomized process of mining (Bitcoins are created through digital mining). 

It's a fairly long blog post, so I'm not sure it makes sense to copy it here; see Bitcoin by Analogy for the rest of the explanation.