Twitter set off alarm bells across the web in recent weeks when it ended its partnership with LinkedIn and reiterated its warning that it would be cracking down on the terms of its API. The company didn't offer any explanation for why it removed tweets from LinkedIn, but speaking with sources familiar with the company's plans, The Verge has learned that major changes are coming in the next few months which will move Twitter from an open platform popular among independent developers towards a walled garden more akin to Facebook.

The moves were not unexpected, as Twitter had announced in March of 2011 that it would not allow services which "mimic or reproduce the mainstream Twitter consumer client experience." Still, it had largely done nothing to the numerous clients — like Tweetbot, Tweetie and Twittelator — which replicate its basic experience. Developers had been hoping for the best and waiting for the other shoe to drop. Last week's news sounded like those dire footsteps. "Whatever perceived gains that might be achieved by eliminating the third parties should be weighed against the lingering public perception that Twitter got greedy," said Andrew Stone, founder of Twittelator. "And like the mythological Greek Titan Cronos, began eating each of his children as they were born."

"All of the good will people associate with Twitter could be tossed overboard."

Twitter won't become a walled garden disconnected to the open web. But the company leadership does believe the best way to attract big brand advertisers and create meaningful revenue is to adopt a closed ecosystem, similar to Facebook, in which users access the service mainly through the company's website and mobile apps, rather than third party clients. The company doesn't want to deal with fragmentation across different services, where it would have to work with API partners to ensure advertising and rich media was being properly displayed. This would become increasingly challenging, as sources familiar with Twitter's plans say that it's hoping to bring a number of new services into the Twitter stream, everything from booking a restaurant reservation to purchasing an item to playing a game.

For developers building on top of Twitter's API, which the company has long maintained will be an "open platform", this amounts to a betrayal, on both a commercial and philosophical level. "Twitter has become a critical piece of our communications infrastructure by making promises about how they would operate," said Nova Spivack, creator of Bottlenose, a social dashboard that relies on the Twitter API. "The question now is whether they will continue to be responsible stewards of our data and that ecosystem, or if they are going to abandon that if favor of a closed business."

"Twitter wants to be a media company like Facebook."

Spivack, like many of the company's critics on this issue, has a vested interest in Twitter maintaining an open and permissive API. His company, Bottlenose, is one of many third party services that tries to augment the Twitter experience with refined social streams and controls. But he also argues that limiting the places in which tweets can be shown is harmful to Twitter's bottom line.

"Why would Twitter limit advertising to its own website and apps when it could show them across the entire universe of sites and services that currently interact with its API?" At that scale, Spivack writes, this solution would transform Twitter’s vast third-party app ecosystem into a massive ad network. "Twitter will almost instantly become as big as ad networks like AdSense and Doubleclick, and would soon rival Facebook and possibly surpass it in advertising reach. It’s a slam dunk for Twitter, and for the ecosystem as a whole. Everyone wins. There is no good reason NOT to do this."

Those who work closely with Twitter, however, don't agree. Mark Suster, a venture capital investor, sits on the board of DataSift, one of only two companies authorized to re-sell data from Twitter's firehose, the full feed of more than 400 million tweets per day. "At the beginning, Twitter was happy to have anyone building on top of their data. That has changed, and if you didn't see this coming, then you haven't been paying attention. Twitter wants to be a media company, like Facebook, and it believes the best way to do that is to tightly control when and where people can access its content."

Popular third party Twitter clients like Tweetbot allow users to "mute" messages they don't want to see in their stream. And third party services like Embedly make it possible for users to embed rich media in their tweets. Twitter wants to ensure that its advertising shows up when and where it wants, no filters or mute buttons allowed. And it's working with publishers to create expanded tweets, a premium service it would rather not be offered by others.

John Borthwick, CEO of the New York based innovation lab, betaworks, was an early investor in both Twitter itself and third party clients like Tweetdeck. "I believed the API could ultimately create a bigger business than media but that question is academic at this point," he told The Verge. "Twitter turned down a path about two years ago and they continue to walk down that path. I hope they are successful at creating this new kind of media business. If they do restrict third party clients I hope they (a) build great clients (b) let third parties pay for access to the API, at a price that the company is excited to have them develop on Twitter. This doesn't need to be setup as a zero sum game."

Third party clients are preparing for the worst. "Twitter obviously wants to make money by advertising in the stream. This will be impossible if all of the mechanisms aren't implemented to spec within a client. They need full control of how the information is presented, and do not have the bandwidth to micromanage ads with third parties to prevent fraud, poor presentation, etc," said Ollie Wagner, a designer for Twittelator, a third party client. "Do I think they'll pull the plug on the API? No, not necessarily. But it may mean they'll become so restrictive that third parties will want to pull it themselves."

If things do get that rough, expect a lot more drama. "The early adopters who have tasted the fruits of polished third party clients are also the key influencers in media, print, television and digital, and the backlash would be swift and lengthy," said Andrew Stone, Twittelator's founder. "All of the good will people associate with Twitter could be tossed overboard if you piss off the trend makers and rock stars. And I bet the guys at Google+ are just rubbing their hands together in expectant anticipation of just such a mistake!"

Additional reporting by Tim Carmody