Dave...I think you deserve a prize or something! To my knowledge you are indeed the first one to crack a disc since we released these kits last summer.
Discs are indeed a wear item. On a car that is tracked frequently, the discs will
always crack before they wear thin. Just to be clear, Dave wasn't posting to complain about the disc cracking. He was posting to say, 'Wow, these discs take a beating.' He has been intentionally pushing the limits of the brakes just to see what they could take. If you look back at his post about the CL pads and the temp strips, he was intentionally pouring as much heat as possible into his brakes. That's why he called it his, 'braking antics.' Dave is slightly warped and likes the idea of being the worst case scenario.
In Dave's case, if he wants to continue his 'antics,' a brake duct kit would likely bring his temps down a bit...or he could purposefully take it out of destructo mode and drive like a normal human-being. :p