Does Technology Limit Tennis Tantrums?

Mercer claims never to stay out late drinking when he's on tournament duty. But he did let one anecdote slip. "In the old days, there used to be an umpire's cocktail party, believe it or not, at lunchtime," he said. "Some of the officials would have the odd sherry and gin and tonic and there was a lady who fell asleep."

Behzad Taidi

U.S. tennis doubles specialist Bob Bryan prepares for the Boodles Challenge event outside London.

Tipsy or stone-cold sober, the human eye just can't always handle a 150 mph serve. Umpires might be right a little more than players, but they're far from infallible. Does Mercer think he was always right when players questioned a call? "Not always," he admitted. "There were quite a few times when, to be honest, I wasn't sure."

And tight calls do matter. They can turn a match. So most players like Hawkeye. Their career and bank balance aren't going to be affected by human error, by a bad call.

"Yeah, the human element is taken out of it," Bob Bryan said, after he finished bashing balls around at ridiculous speed. "But these are huge tournaments. There are huge purses on the line."