It seems like the time to start pricing things millibitcoins might be approaching already.
At the current exchange rate of $31, a dollar is 32 millibits.
There are already quite a few foreign currencies worth the same or less than a millibit, 18 listed here:
http://www.x-rates.com/table/?from=USD&amount=.031Including the yen and ruble.
I would expect that bitcoin adoption would increase if the exchanges, wallets, and shops showed prices in millibits today. Why? Because everyone's first foray into bitcoin is buying them, not selling them. So $31 each sounds expensive, even though prices *in* bitcoin sound cheap. No one cares how few bitcoins you can trade for a can of coke, unless they already have some bitcoins.
There are already places that price things in millibits, and you can choose how amounts are displayed in the client so you can use millibits all you want. All it takes is people actually quoting prices in millibits and it will become the de facto standard.
US Dollars are currently going for about 31.8 mBTC each.