The basic arguments are that users get an inconsistent experience depending on where they view a user’s timeline, profile or how they interact with the Twitter services. Basically, it’s consistency, consistency, consistency.
As I see it
The way I see it, and this may be blunt: it’s about monetizing. By not encouraging developers to build new apps or services accessing timelines, and by having way more strict guidelines for existing ones, it appears it’s only about driving traffic to the Twitter web site and apps. By owning how data is presented, making money through ads or other services becomes a much better possibility.
And no, making money is not evil. I understand they need the revenue and that they are a business. But what gets to me is that third party apps is what made Twitter so huge, and by trying to control them and herd them in just the direction Twitter wants, it drastically cuts down on user choice. And asking developers now to build other types of apps in the Twitter ecosystem doesn’t really seem helpful, and as a developer, I would just wonder when they would start cutting down/controlling those areas too.
What makes a service rich, for both developers, and more importantly end users, is having choice. User both need and deserve diversity, and that is what the web is about. It’s about content and services, and how people like to use it – not just presentation. For companies to be able to achieve this, they should offer an open API where anyone can develop the services they seem fit – and naturally, this is not something which should later on be cut down.
I’m also afraid of the possible repercussions from this in terms of developers being wary of using various services’ APIs to build amazing things. Combining content and cross-presenting can make a web site or similar great, but if people get wary of using content/possibilities provided through other APIs, it will make us miss out on good experiences.
I sincerely hope Twitter backs down on this, and finds other ways to reach the goals they want.