Twitter has infuriated developers by changing its policy on who can build applications on top of its service.
The social network has an API which allows other companies, apps and services to incorporate Twitter into their products.
Until now it has been relatively easy for developers to use the API, with few restrictions, despite Twitter's previous warning that programs should not try to replicate its own client.
But the new announcement says third-party clients will only by allowed a maximum number of users.
Michael Sippey, on the company's dev blog, explained the new policy with a four-quadrant diagram, outlining what third-party apps it wanted to encourage:
"With our new API guidelines, we're trying to encourage activity in the upper-left, lower-left and lower right quadrants, and limit certain use cases that occupy the upper-right quadrant.
In the upper right-hand quadrant are services that enable users to interact with Tweets, like the Tweet curation service Storify or the Tweet discovery site Favstar.fm.
That upper-right quadrant also includes, of course, "traditional" Twitter clients like Tweetbot and Echofon.
Nearly eighteen months ago, we gave developers guidance that they should not build client apps that mimic or reproduce the mainstream Twitter consumer client experience." And to reiterate what I wrote in my last post, that guidance continues to apply today."
The new rules mean current clients can only have double the users they have now, and that new clients can only have 100,000 users unless given specific permission by Twitter.
The maximum growth limit could be disastrous for new and existing businesses, which rely on new users for revenue and investment.
It will also change the number of calls on Twitters servers that clients can make when refreshing tweet streams, searches and profile lookups.
Other changes will affect the way Tweets are displayed on external sites. Third-party clients will have to display a user's avatar and username, and will not allow "other social or 3rd party actions (to be) attached to a Tweet".
The new requirements have to be met within six months.
Developers and tech insiders have attacked the new policy for "killing off the third-party ecosystem".
The Next Web said it would irrevocably change how Twitter works:
Matthew Panzarino at the website, wrote: "There's no way to sugar coat it. These changes effectively kill off the growth of the third-party client ecosystem as we know it. Twitter wants people to be using its official apps and seeing tweets exactly as they're displayed both there and on the web version of Twitter."
Meanwhile John Gruber at Daring Fireball said it was "a huge discouragement for starting any new Twitter clients".
However, some developers were not as worried.
Paul Haddad, who runs Tapbots and their popular client Tweetboot, said (via Twitter):