The casual wave after a net cord winner is the most disingenuous gesture in the game. It's also a reminder that tennis is, at it's core, (as Cindy said earlier) a gentlemen's game. Although an anachronism, it's often expected, and since there's little effort involved in making the gesture, why not do it? Among my frequent partners though, there's no wave or apology. We go straight to the Bartoli fist pump, and punctuate it with a "yeah!"