A "cent" doesn't require moving the decimal point of the currency, it's what we already use:
1.00 = bitcoin
0.01 = bitcent
A "centibitcoin" (and that would be technically correct) would be too close in value to the existing currency, making mistaking one for another too easy.
SI units are commonly used as primary designators, and two uses can perceived as different words:
microfarads = capacitance
centimeters = length
kilometers = length
However, there are no examples of SI units with currency though, because there have been few times in currency history where small units have bought so much. US Dollar in 1850-1900 is equivalent to Bitcoin now. If we divided bitcoins into eighths:
"Shave and a haircut, two bits!" = $0.25 in 1900
"Shave and a haircut, two bits!" =
BTC0.25 in 2013 ($11)
"Bits", or pieces of eight, is a term that comes from a time in colonial America when a silver coin was too much money to be used. Fortunately we don't have to cut up a bitcoin to spend it.
For large amounts, language already has it's own "SI" units, million, billion, trillion. "The US budget deficit is $845 gigadollars" is not said.
I think we have another three decimal places of valuation to go before BTC becomes burdensome, making it difficult to visually discern decimal places on a number like .000051 bitcoins. After that,
microbitcoin would be the logical unit to use, as a unit that is
one million times smaller is a big enough divide that both currency designations won't be commonly used at the same time, and an error in the amount will be easily noticed - "oops, I accidentally sent you 10,000 BTC instead of 10,000μBTC" just isn't going to happen. A satoshi is a microbitcoin cent.
"Who wants to be a microbitcoin millionaire?" = 1 BTC