Billion, with a B. An email to every single one of its users—so actually a little over a billion at this point. In other words, one seventh of the entire Earth's population is getting hit with one message.
The blast—the largest email dispatch Facebook has ever sent out in its history, and certainly one of the biggest non-spam deliveries in email history—isn't even of anything particularly thrilling. In short, Facebook used to allow users to vote on certain policy changes if enough people chimed in—now they're going to phase that out, which doesn't matter because nobody really used this system anyway.
So as not to cause some sort of explosion, Facebook told us it'll be sending the messages out in waves But still! One billion emails. One billion people, hypothetically all reading the exact same thing. How many times has that happened in human history? I would venture not that many times! Of course, if you add in all the people who will die between now and then, spam filters, people who just delete everything, and those mutants with 95,000 unread messages in their inbox, the number will be lower than 1,000,000,000.
But I repeat: a billion damn emails. If you listen closely, you can hear them rumbling right now.