How Snow Leopard reports drive capacity
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I think it's a terrible idea. This will break capacity calculations for many apps, potentially leading to inconsistency in space and size reporting between different programs running on the same system.
It will also lead to file size confusion when moving files between OSes.
There is some justification for measuring RAM in GiB rather than GB: The design of RAM chips makes this far more convenient. But there's no reason for anything else to be measured in "binary" capacities.
Also, the GPU and ethernet argument is off base (no pun intended); CPU speed (in Hz) is based in units of s^-1, so it wouldn't make any sense to redefine that in base 2. Ethernet speeds should probably have been measured in base 2, but the numbers are so widespread now it would be confusing to change it.
http://en.wikipedia.org/wiki/Binary_prefix
4GB (SI) == 3.7GiB (binary)