Keeping an API stable is a surprisingly large amount of work. I've never worked with a codebase as large as Twitter's, but I have seen that even with testing in

Keeping an API stable is a surprisingly large amount of work. I've never worked with a codebase as large as Twitter's, but I have seen that even with testing in place it is easy for seemingly unrelated changes to break the API. If Twitter has reduced engineering staff, API functionality would be one of the first things to suffer in my estimation. This doesn't manifest as someone purposely breaking the API, but incidental changes breaking it. For example, a minor change in something like time display code that does the "posted X minutes ago" could easily end up silently corrupting API calls in odd ways. And if the engineering staff is reduced, fixing the API that broke a 3rd party vendors product will likely be a very low priority.