I don't know for sure what the original problem was, but the most recent issue was a result of implementing [a new badge](https://meta.stackoverflow.com/questions/341214/introducing-the-silver-census-badge) without rebuilding the API. Once the API was pushed to production, the bug was resolved. If it happens again (especially if there's a new badge) please let me (or really any employee) know. We can contact a developer directly.


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From [a comment on a related question][1]:

> Fundamentally the problem is that the API can remain broken without us really paying attention to it. I appreciate your report since it prompted us to rebuild the API. (That was the immediate problem this time around.) But **we shouldn't really be relying on user reports for this sort of thing.** 
>
> **We need to start [treating our products as a platform][2].** We don't treat our API as mission critical. There's good reasons for that, but it's going to hurt us if we don't sort it out eventually. (Summary: sorry about that. We can do better.)


  [1]: https://meta.stackoverflow.com/questions/341926/census-badge-link-404s/341928#comment435402_341928
  [2]: https://plus.google.com/+RipRowan/posts/eVeouesvaVX