I understand it would take some wildly low probability events for it to be needed, but could we double the precision if needed? (Just trying to figure out if it actually could be a significant global currency).
e.g. - There are $1.19 trillion of US dollars in circulation. Assuming that USD cap = BTC cap, and assuming 21 million coins, that means that each coin would be worth $56666.6666667
Taking it a step further we assume today that we can do at least to the penny, but many times one tenth or one one hundredth of a penny.
At this point $1 would equal = 0.00001764705882 btc.
So, 1 penny would = 0.0000001764705882
1/10 of a penny would = 0.00000001764705882
1/100th of a penny would = 0.000000001764705882
See the issue? If bitcoin become a viable currency, we'd need to carve and carve in ever smaller pieces to the point a satoshi is equal to or greater than a real world currency unit.
-helixone
P.S. - Of course I realize that btc would fail in many other ways before it could handle the volume of transactions the USD does. (Not related to precision).