Yeah I was on the baseline and right in back of the line judge and he missed a call that was over ruled. He looked bad, but he's human and it's a tough job being focused like that, where you have to turn it on and off with each point.
What I can't figure out is what the line judges say, if they're not saying "out".
The Serena Williams line judge, you know, from the US Open, just seems to make a loud grunt that is totally unintelligible.
Its bad enough to warrant more challenges per player... also think you should earn a challenge for for being correct when officials are wrong! Take one away for being wrong give them one for being right...