Thanks, Moxie (for the "drag"). But I am sure you can do it in less than one minute, Formula 1 teams change the four wheels of a car in less than 2 seconds -- anyway, just thinking out loud.
About Hawkeye and grass, I guess there is a combination of factors. As you say, the fact that the surface is not smooth is a factor, and, again as you say, on grass it shall a problem too. I am pretty sure the accuracy on grass is smaller than on hards.
But clay has two additional problems. The dust, which goes up after the ball touches the ground, and surely blurs the image. The physical condition which defines the instant of contact is the inversion of the vertical speed orientation -- and surely the raising dust makes this a little harder. Also, the color of the court. In the end, all is translated to pixels, and optically orange is composed by yellow and red. In other words blue and yellow have a stark contrast, orange and yellow don´t. (see, the solution is blue clay. I keep saying but no one listens!!!).
[Edit] Of course I would not resist and try to answer your rhetorical question.
A match rarely hinges on one bad call, however dismal and impactful, as in this case, on the one game. The momentum really shifted after that game, but you get a reset in the next set, and there were two sets left. Also, on Tennis Channel, Mary Carillo (who I generally like) was very upset, and thought that Rafa should have conceded the point, and after the match maintained that he should have apologized to David. That's both ridiculous and unfair to Nadal. He was prepared to accept the out call, but Mourier overturned it. He was far away from where the ball landed. It would have been odd to go against the chair, from where he stood in relation to the ball. 
) Hawkeye works because the players accept what it shows them. Also, it speeds things up, in part because it eliminates arguing. Isn't that one of the things the game is trying to do? I've always been happy to keep it old school on clay, but I'm beginning to change my mind.
