To be explicit about some of this fail... it never ceases to amaze me that the people trot out the 'deflation/depression' "problem" apparently without considering what that implies.
It suggests they are worried about the scenario where Bitcoin is the main currency of entire nations or even the globe.
Really? Their main criticism of Bitcoin is that they think it could be so wildly successful that the 'money supply' will be threatened by its deflationary nature?
To be clear - Due to divisibility, I'm not convinced it would be a problem even if Bitcoin was the primary currency, but people comparing Bitcoin's deflation to historical deflation/depression scenarios seems to be treating Bitcoin as a replacement currency set to dominate the world rather than just another currency or commodity amongst many.
I've looked into the divisibility for another project representing people using fractions of BTC, here's my notes:
...this leads to some interesting possibilities. Assuming that we aren't dealing with the minimum unit - you could represent every person in the united states with one vote (Jul 1, 2011 311.59 million - U.S. Census) for the amount of:
0.0000001 = 10 million 'votes' per 1 BTC
You'd need: 31,159,000 fractions to represent the US population, which equals:
31,159,000 x 0.0000001 = 3.1159 BTC
That's quite heady of a concept, and it wasn't even the minimum divisible unit!
. 
