[vark]

Adding a Y axis would immediately draw up hundreds of blog posts and academic papers citing it as a "benchmark", making various claims and hypotheticals about Facebook's infrastructure. Since we don't have access to the exact metric or method of measurement, the exact magnitude is arguably meaningless.

Also, since this has potential for FUD and Facebook-bashing, it's in their interest to not publish raw numbers.

[jacobolus]

Or they could just leave out the graphs altogether. As it is, they’re pretty much useless.

[kdeberk]

No it's not useless since it also includes yesterday's measurement for that same timeframe.