Rationally, the Twitter API changes and developer rules are entirely logical and consistent within Twitter’s larger vision. Twitter is consolidating power and (in my estimation) aiming for an Apple buyout. Getting a grip on their user experience seems to indicate their intentions as much as anything.
But if you approach it not so rationally (and I do) it’s a slap in the face to the developers and early adopters who made Twitter what it is; often literally. The @-reply and hashtag are both user conventions. Things like the lesser known cashtag and early implementations of lists come from users who wanted to extend what appeared to be a next-generation communication mechanism.
Again, rationally, Twitter is totally within their rights to embrace, extend, and extinguish these user improvements. Twitter never professed to be an open communications platform: it always had API rules and guidelines and the protocol itself was never actually a protocol. It was (and is) a closed source utility that we were naïve enough to assume needed us and our contributions, be they API implementations or simply new use cases.
Turns out we were wrong. Maybe it’s time we start reconsidering our reliance on closed source walled gardens.