I appreciate the jest of your comment, but I think it's a bit disingenuous to dismiss the 1 billion number because a small fraction of users may have multiple accounts.
Because let's be fair: Facebook is one of the very few companies that announces active users, with a fairly clear definition of what they mean by "active". At this point they're likely to have more accounts (including unused ones) than there are people alive so it would be silly now, but they've virtually always used the active metric.
Because let's be fair: Facebook is one of the very few companies that announces active users, with a fairly clear definition of what they mean by "active". At this point they're likely to have more accounts (including unused ones) than there are people alive so it would be silly now, but they've virtually always used the active metric.