40 percent of Twitter users have not tweeted since their first day on Twitter

"- 40 percent of Twitter users have not tweeted since their first day on Twitter, evidence that the account was most likely created and subsequently abandoned.
- Approximately 25 percent of Twitter users are not following anyone, while two-thirds are following fewer than 10 people, evidence that the account was created but is largely dormant.
- More than one-third of Twitter users have not posted a single tweet, and almost 80 percent of users have fewer than 10 tweets, evidence that while Twitter is billed as a great collaboration tool, a large number of users are there to consume content, not distribute it.
- Approximately 30 percent of Twitter users do not have any followers, and 80 percent of Twitter users have fewer than 10 followers, evidence that for many users, their posts are not being widely tracked or read.
- 50 percent of Twitter users are following more people than they have as followers, and another 30 percent of Twitter users are following the same number of people that are following them, evidence that users are aggressively trying to attract followers by hoping they will “follow back” but have been unsuccessful."
Source: Press Releases from Purewire, 8th June 2009, based on analysis of 7m twitter accounts
This research backs up an earlier report from Nielsen saying that about 60% of twitter users abandon the service within one month, whether through the twitter site itself, or an external application.