A Twitter account has gone offline (Poker_Flat in this case) around 01:00 AM UTC time 09/11/2012 (dd/mm/yyyy) and this breaks the /users/lookup API request with a 500 (internal error 131) problem.
If you try to access it directly on Twitter, you get an error page:
This would not normally be a problem, but it completely breaks the API request for /users/lookup if this user name occurs somewhere in the list of 100 users that is posted. Surely this is not correct behaviour? It becomes almost impossible to detect why the request failed without going through manually trying each name one by one until the problem user name is found. Instead the API returns a 500 (internal error 131) which doesn’t help diagnose the issue. What could cause this issue?
However, if I try to access an unknown or non-existent user name somewhere in a list of valid screen_names in the users/lookup, then there is no problem, and that unknown user name simply isn’t returned in the list of user objects.