At its 2011 f8 developer conference, Facebook co-founder and CEO Mark Zuckerberg today announced that Facebook hit a new milestone: half a billion people used Facebook in one day. That's right: 500 million users logged onto Facebook in 24 hours.
Let's put that into perspective for a second. Just two months ago, Facebook confirmed it had over 750 million monthly active users (update: actually, it's 800 million). Now it's at 500 million daily active users.
The next official number will likely be 1 billion users. After that milestone, the next one will be passing India, and then China. If Facebook was a country, it would be the world's third largest, by population.
Plenty of websites only report cumulative users, which does not take into account inactive accounts. Facebook's user count metric is much better as it is defined as a user who has logged in within the last 30 days (or in today's case: one day). This does not eliminate the issue of one person having multiple accounts, and that's why the social networking giant bans 20,000 accounts per day.