Bitcoins are 50 times more valuable today than when I first heard about them six months ago. If they just double in the next six months, they'll have risen 100-fold in a year.
It seems like a good idea to me to come to a consensus now about when to "move the decimal points" -- when should the Bitcoin program allow you to specify payments with more than two decimal places (e.g. "pay Gavin 0.001 BTC for his thoughts") ?
When should the Bitcoin program assume you're entering payments in 'millicoins' or 'microcoins' ?
And when should all of the internal minimums (e.g. smallest transaction fee or the trigger for the 'micro-transaction spam prevention') be lowered?
Here's a straw-man off the top of my head:
When Bitcoins are worth more than about ten dollars (or euros) each, I think it'll be time to allow sub-bit-penny payments. And I think the "smallest free transaction" limit (and other internal minimums) should move in lock-step with that change.
When 1 Bitcoin is worth somewhere around $100 (in 2010 dollars), I think it'll be time for the client to switch to millicoins (e.g. .001 BTC), so if I'm buying a paperback book it costs 50 milliBTC instead of .05 BTC.