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?
I think we should allow three decimals now, to make very small payments possible, and have a default fee of one millibitcoin for transactions smaller than 0.01 to discourage overuse. Note the use of millibitcoin to make people used to the word. It should be configurable in the client to use bitcoins or millibitcoins as the default unit in the client, but for the time being it should default to using whole bitcoins.
Use familiar SI prefixes. I do not think bitcoins should be used as a means to introduce an entirely new notation like BTC4 or B4C or whatever. The concept of Bitcoin is hard enough to grasp itself for beginners. While it s intuitive to most people that a microbitcon is the same as 0.001 bitcoin, just as one millimetre is 0.001 metre and 1 millilitre is 0.001 litre, it is not at all obvious what those alternative notations mean.