Yep. Half a billion. Impressive, right? That’s half as big as Facebook. Except… it isn’t. Facebook’s 955 million tally is based on active users – I’ve speculated in the past as to how many total users Facebook has (that is, anyone who has signed up at any time), but it’s likely now well above two billion, which, by any count, is a lot more than Twitter, who revealed it had just 140 million active users back in March of this year.

That number should be quite a bit higher by now, but it hasn’t leapt up to 500 million, which was the figure proposed by Semiocast in their study. Which means that (approximately, and assuming growth over the past six months in actives) around two-thirds of Twitter’s total user tally is made up of inactive accounts.

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