With Twitter's supposed IPO coming up "by the end of year" its size and sustainability have become a point of much debate. Today a study from Columbia Business School and the University of Pittsburgh gives us a pseudo answer on the question, alleging that Twitter has 500 million users and therefore is big. Twitter, said Columbia Business School professor Olivier Toubia, "isn't just going to disappear. It's just going to become a new way to follow celebrities, corporations, and the like." Arguably that's already Twitters purpose for a lot of people. But let's get back to that 500 million number: Is that really so big that Twitter could never disappear?
Something like only 16 percent of the Internet population uses the service, according to this year's Pew Study. That's up from 13 percent a couple of years ago, but still pretty bitty. Compared to other social networks, however, Twitter just about falls in line, as you can see in the chart below. As of December 2012, Twitter had 200 million regular users, besting Instagram and falling about 100 million users short of Tumblr.
With Twitter, however, one has to consider that "monthly active user" numbers also includes a fair amount of spam bots. In addition some real-life individuals have more than one Twitter account. Generally Facebook users have one account to represent themselves. But even if that knocks out some hundreds of thousands of users, Twitter still does alright.