I ain't buying it anymore. It's not the heat, cold, temperature fluctuations, cleaning method, pin drilled to close to finger hole, super glue etc, etc. Some balls crack, some don't.
Personally, I believe it's a manufacturing flaw within the shell of the ball that causes it 99% of the time. The ball companies all have a stake in us believing "it's OUR fault". No it isn't, it's a quality control issue in their process.
Of course, there is the occasional genius who "butterballs" a ball in the oven, but that results in a completely different crack pattern than a ball with a single crack all the way around.
Then again, I could be wrong.