According to data published by Twitter analytics firm Twopcharts, Twitter may have a stickiness problem. According to the data there is a large discrepancy between the number of accounts created and the number of accounts that actually remain active. Of the 284 million accounts created in 2013, only 37 million (12.9%) were still actively tweeting in February 2014. On the other hand, of the 4 million accounts created in 2008, 1 million were still tweeting in February 2013, indicating that early Twitter adopters are more likely to stick with the service.
In case you are wondering how 284 million accounts can have been created last year when Twitter only has 241 monthly active users: According to Twopcharts, there are around 980 million Twitter accounts, of which only a small fraction is actually active.