To use an analogy, imagine if someone wrote: "$1.5M B" instead of 1.5 quadrillion or 1,500,000,000,000,000. You'd be confused, and rightly so. A lot of people would mistakenly read it either as $1.5M or $1.5B, neither of which is right.
In this case a lot of people are misreading it as 1.5 GB/Day instead of 1.5 PB/Day.
PS - The way Google uses it in the Blog post is pretty clear, they're describing what a petabyte is. My issue is with the HN title only.
I'm sure I'm strange, but I find "$1.5M B" clearer than talk of "quadrillion"s, because I'm not confident I know what power of 10 a quadrillion is, but when I see M B I just add 6+9. Even then, the British sometimes say things like "thousand million", because billion over there used to mean 10^12, but now means 10^9 (which they used to call a milliard); as with other wordy number-words they've succumbed to American usage¹.
M is well-known in headlines as million. A GB is something people appreciate the size of, TB not as much, and PB is definitely not in most people's vocab.
In which case it doesn't get combined with an SI prefix because the financial "M" is not the same as the SI Mega. Jamming two SI prefixes together is plain ignorant.
Oh, come on. This is a bullshit argument. Hacker News does not have the same audience as The Daily Mail.
Nobody measures things in megagigabytes.
To be truly pedantic, "M" can also mean "mille" or thousand if you're talking about things like CPM. Mixing units like this introduces needless confusion when there's already a SI unit for the job: P.
