While it has been covered in many other places across the Web (start with Marco Arment, then Ben Brooks), Twitter’s API changes today should worry any social marketers who use tools and technologies that interact with Twitter.
In Twitter’s announcement, they state that they are not going to penalize “Enterprise Clients” and vendors of “Social Analytics” — every quadrant but the top right of their visualization, below. However, Twitter did not clearly delineate lines between what is and is not acceptable. To continue to grow, Twitter needs to encourage a robust and healthy ecosystem, which supports both marketers and users. In order to do that, Twitter must provide much clearer guidance about the long-term stability of its APIs and its support for businesses built on top of their data. If this requires announcements of additional fees for data usage, that will be fine as long as the rules of the road are clearly laid out.
Until Twitter does so, I expect the volume of new enterprise-ready startups centered on Twitter to reduce, and existing vendors will increase their focus on other platforms and communities as CEOs and boards of directors try to reduce their risk and exposure to future changes by Twitter.