As tansey said Big-O for the worst case would be O(inf), Best case is O(1), if n is the length of the list, because if the sort returns the speed is independent of the size of the list. The average case is a little harder, but based on the 140 character limit someone else mentioned, I would say that the average case would be O(inf) cause on average it probably wouldn't correctly sort the list.
The speed is definitely not independent of the size since you still have to write a string of size O(n).
The probability of the original input list being in the exact order it's in is 1/(n!). If that's the order you wanted then the algorithm might very well approach O(0).
It's O(whatever algorithm the responder uses), plus a HUUUGE constant for latency and wrong answers.