I don't know much about it but I thought only hardware manufacturers used MB for marketing purposes. And I thought all softw based measurements were in the 'TRUE' measurements. ie: one megabyte 1 MB = 106 B = 1 000 000 B
one mebibyte 1 MiB = 220 B = 1 048 576 B

So in that light I thought you should be using mebibytes or its equivalent. I'm surprised Gnutella uses the other!

But then again, I suspect on the mac there's a lot of rounding off that goes on.