Depending on your world view, it could either be the greatest tennis innovation since Hawk-Eye or a sexist, exploitative blight on one of the premiere tournaments on the clay-court schedule.
Either way, models are still serving as ball-girls at the Madrid Open.
In 2004, organizers of the Madrid Open hired models from a local talent agency to serve as ball-girls during the men's Masters event. There was the predictable carping from local politicians, stories about whether the women were qualified to be on the court (they were trained for two weeks, which actually seems like a lot more instruction than any child would have received) and a bunch of pictures in which male tennis players were possibly checking out the talent.
It is a little strange to see leggy women in their early 20s prancing around the court (that's not a sexist comment, a majority of them really do gallivant around the court as if they're still wearing their usual Fendi heels), as they do things at the deliberate speed you'd expect from a model chasing a tennis ball. It's slow enough to get noticed, but quick enough so that they exert the exact amount of energy necessary to make sweat glistening rather than drenching. One always gets the sense they keep one eye on the video screen as they watch themselves gavotte.
Though tournament organizers can do what they want in regards to ball-girl hiring practices, the time has probably come to send the models back to the runway. As a publicity ploy, this worked wonders in 2004. Six years later, the controversy isn't there. The best way to produce some headlines now would be to bring back the energetic youngsters.
Eh, maybe in one more year.