Fred, the picture is inboard, but damage is on both sides. Your explaination makes sense, but if you look at my photo more carefully, you will see that there is a hairline crack in the middle as well, not just on the outside. Maybe Andrew@SouthernBM can confirm this but I believe he told me that they were crumbling inside as well.
Taka, don't worry about buying one of these cars. Just like you have put AP Racing brakes on your RX-8 race car, we should be doing the same thing on this car. I intend to do that at same stage and the time will depend on where we get to with this current issue. If it's a problem with the piston disintegrating completely, then AP Racing brakes will go on asap. If it's just the ceramic insert as Fred mentioned, then I am happy to leave it as is.