I voted 3, but again, it's not confusing, it's just unnecessary, and comes across as pedantic and frankly a bit pretentious.
I agree with mroz, it's not about being scientifically or technically correct, it's about semantics, specifically, about pushing one set of standards instead of generally understood established useage. It may have a use within the scientific computing community where it's important to be very clear which units are being used (however, even there everyone knows that bits and bytes are counted in base 2, not 10, so if the unit is b or B, then k does mean 1024), but I see absolutely no need for it in a consumer-oriented website.
In any case, as with many things, Dan of Dan's Data probably has the proper take on the matter:
"SI unit enthusiasts have recently managed to kick up a burst of media coverage concerning their campaign to get units of computer memory referred to as "kibibytes", "mebibytes" and "gibibytes". This campaign would seem to me to be doomed to failure, though, partly because those terms sound much the same as the old ones, and partly because they sound silly."