Developers ... be gone! Getty / Scott Olson Twitter has taken the unusual step of shutting off its datapipe to certain companies that have published their own stats on how big Twitter's user base really is, according to two sources.

The move comes after Twitter's stock was hammered in the early part of the year when investors discovered growth in monthly active users (MAUs) was slowing or stagnant, and that measures of engagement per user were on the decline.

Since then, Twitter CEO Dick Costolo has ordered a revamp of the Twitter user interface in order to make it easier and more attractive for people to use. He also reshuffled his management ranks, getting rid of a COO with largely financial background and replacing him with a product chief from Google.

At the same time, Twitter's stock price rose nicely. Some analysts see it hitting $60 a share (see disclosure below).

But third-party companies that published their own measures of Twitter's user base were a thorn in Twitter's side. While Costolo touted the company's growth to 255 million MAUs, Business Insider was able to report that the number was only a fraction of the 1 billion people who had tried Twitter.

Most people who sign up for Twitter abandon it, it seems. Also, most people on Twitter don't tweet, according to third-party apps that accessed Twitter's data firehose.

Now, companies that used to provide that data have been axed from Twitter's application programming interface (API), the firehose of data that software development companies can plug into in order to build useful products for Twitter and its users.

Twitter declined to comment when reached by Business Insider.

We don't know why Twitter has begun culling developers from its API, but one theory might be that it has nothing to do with wanting to restrict who sees user data. Rather, Twitter has been slowly building a very nice data business of its own, which will probably book $100 million in revenue this year. The company may simply have decided it is time to end the free ride for developers who give away for free what Twitter would rather charge for.

"They shut me down last Friday night after the market closed," one developer told Business Insider.

Another developer, Twopcharts, is currently displaying this sign on its web site: