Twitter has announced a series of upcoming changes to its API that could cause problems for developers who use it their apps.
There are a number of technical and aesthetic updates, but the biggest change is that certain calls to the API will be rate-limited and governed by authentication tokens, which means that any developers signing in to the Twitter service will need to monitor when they're logging in and how.
Also, Twitter is going to be enforcing certain "display requirements" in order to get developers to conform to the service's look and feel. In Twitter apps, these things aren't a big problem. They ask that the "@" symbol is always used with usernames, and that retweet, reply, and favorite buttons are always clear and in the same place. But for apps that use Twitter's API in other ways, that might not be so easy.
The good news is that the developers of two big third-party Twitter apps for iOS have already confirmed that they're ready to work with the changes. Tapbots has put up a blog post saying that it shouldn't have a problem complying with either the authentication regulations or the display requirements, and that it will work with Twitter to make sure things go all right on both iOS and Mac. Ged Maheux of Iconfactory has also confirmed that Twitterific should fall within the guidelines.
It's completely reasonable that Twitter would want to make sure its service is used responsibly and represented well, but a big part of the service's success is its third-party accessibility and interfaces. It sounds like developers were angry about these changes when they first appeared, but Twitter seems as if it's responding to these changes in a reasonable way.