In a second round match at the US Open on Thursday evening, Simone Bolelli and Tommy Robredo were in the third set when a fan yelled so loudly, it was indistinguishable from the call of a line umpire calling a ball 'out'. At the time, the two were in the middle of a deuce point, while Robredo led 5-4 in the set. During the rally, the ball may or may not have been out - but a fan loudly yelled "out!" anyway, and both players stopped playing the point because they thought it was one of the officials. It wasn't.
Ten minutes of drama ensued as the umpire got out of his chair to explain to the players his call, and the umpire's supervisor came out to overrule him. The point was not replayed. Robredo, who was down 2 sets to 0 at the time, won the third set to sent the match to a fourth set. Bolelli, who was the player screwed on the point, pretty much self-destructed from there, as Robredo won the next two sets. The match is currently in the fifth decisive set.
Oh, the drama!
UPDATE: Tommy Robredo has won the match. Bolelli never recovered from the crowd call and lack of replaying the point, despite being up two sets at the time. ESPN also reports that the umpire's supervisor who overruled him and decided not to replay the point was not on the court when it happened, so it's definitely a controversial decision.
Here is a vine of the "out" call so you can hear for yourself.