Twitter on Friday issued a clear statement to developers that placed a moratorium on third-party apps.
Why? When you have to ask "why," the answer is usually "money." But here's the official line from Ryan Sarver, Twitter's "director of platform":
We need to ensure that tweets and tweet actions, are rendered in a consistent way so that people have the same experience with tweets no matter what they are ...
There's a time and place for uniformity of experience. It's called McDonald's.
Twitter's revenue model, if it ever gets its act together, will be the sale of advertising. So yes, I can see why they might API-block apps that don't run the ads they sell.
Beyond that, denying users the ability to tailor their Twitter experience to their own preferences (by denying developers the ability to offer other options) can only hurt, not help, Twitter.
Some people like Twitter's in-house experience (I'm one of them, although I've been flirting with Seesmic lately).
Others want to use Tweetie, Tweetdeck, whatever.
Unless Twitter is playing some deep game in which mass migration to some other API -- StatusNet, for example -- followed by fiery corporate death is part of the plan, it needs to extract cranium from rectum ASAP.