Comment 20 for bug 240073

some more information:

The SI prefixes should only be used in the decimal sense: kilobyte and megabyte denote one thousand bytes and one million bytes respectively, while kibibyte and mebibyte denote 1024 bytes and 1,048,576 bytes respectively. This recommendation has been adopted by SI, IEEE, CIPM, NIST, ISO/IEC and some other leading national and international standards, which now state that the prefixes k, M and G should always refer to powers of ten, even in the context of information technology.
(reference: ISO/IEC IEC 80000-13:2008 )

reduced timeline:
1998:
IEC introduces unambigous prefixes for binary multiples (KiB, MiB, GiB etc.), reserving kB, MB, GB and so on for their decimal sense.

2005:
IEC prefixes are adopted by the IEEE after a two-year trial period.

2008:
NIST guidelines require use of IEC prefixes KiB, MiB ... (and not kB, MB) for binary byte multiples

“The names and symbols for the prefixes corresponding to 2 10 , 2 20 , 2 30 , 2 40 , 2 50 , and 2 60 are, respectively: kibi, Ki; mebi, Mi; gibi, Gi; tebi, Ti; pebi, Pi; and exbi, Ei. Thus, for example, one kibibyte would be written: 1 KiB = 2 10 B = 1024 B, where B denotes a byte.
Although these prefixes are not part of the SI, they should be used in the field of information technology to avoid the incorrect usage of the SI prefixes.”

also remember this:
decimal value binary value difference
1000^1 = 10^3 1024^1 = 2^10 2.4%
1000^2 = 10^6 1024^2 = 2^20 4.9%
1000^3 = 10^9 1024^3 = 2^30 7.4%
1000^4 = 10^12 1024^4 = 2^40 10.0%
1000^5 = 10^15 1024^5 = 2^50 12.6%
1000^6 = 10^18 1024^6 = 2^60 15.3%
1000^7 = 10^21 1024^7 = 2^70 18.1%
1000^8 = 10^24 1024^8 = 2^80 20.9%

also, this has a usability impact, since using the same wording with two different meanings is JUST PLAIN WRONG, and should end RIGHT NOW,
Regular users don't know that the units have dual meanings, and we shouldn't continue confusing them in this way.