Twitter API returns malformed JSON for some valid requests.
I discovered this while attempting to fetch all of my list memberships via the API. The issue is present regardless of authentication. It occurs 100% of the time, and has persisted for over twelve hours. I have reproduced it for multiple users.
Note that the response does not indicate any error condition. The transaction completes successfully, but the payload is malformed.
It seems that any user with enough lists will eventually have a page returned containing this bug. I've located it on the first two users I tried, which is my own account (@idangazit ~120 listed) and that of Jacob Kaplan-Moss (@jacobian, ~500 listed), founder of the Django web framework.