119m twitter accounts follow at least one other person, but only 1.5m follow more than 512 people

"Fortunately, we know someone with full access to Twitter's API. Even more fortunate, this person took it upon himself to have an engineer write up some code and actually count the real number of users on Twitter.
Well, that's sort of what he did. What he actually did was look at follower/following statistics, to see how many users are following or are followed by a certain number of people.
Using data that is now just one month old, he found out that…
There were 119 million Twitter accounts following one or more other accounts.
There were 85 million accounts with one or more followers.
With these figures, and Twitter's claim of 175 million accounts, a little subtraction shows us that there are 56 million Twitter accounts following zero other accounts, and 90 million Twitter accounts with zero followers.
Those are some interesting figures, because they show us Twitter is much smaller than the "175 million!" number might lead us to believe.
But they still don't answer our question: How many active users does Twitter have?
To get close to answering that question with this data, we have to take a guess at how many accounts an "active" Twitter user follows.
At Facebook, a company source tells us, they believe that a user is not going to end up sticking around unless they make friends with 10 people.
So let's say an "active" Twitter user is someone who follows at least 10 other accounts.
How many such "active" Twitter users are there? Our source's API data shows that there are 56 million accounts on Twitter following 8 or more accounts. There are only 38 million following 16, and just 12 million following 64.
Your author, by the way, follows 700 people. There are only 1.5 million accounts on Twitter following 512 or more accounts."
Source:  Data unofficially collected from the Twitter 'firehose', reported by Business Insider, 31st March 2011