I'd like to thank the Original poster to this, in my opinion, a major issue.
I had the car on the hoist today and elected after reading that post to remove the pads and take a look, the photo you see is the one i took and emailed the owner, i have others but they are not as clear as the one posted. The Piston crack is a major issue to me and i am just glad we saw it as the car was to see a track tomorrow night, there are other cracks visible but the one you see is more than a crack, the piston has come apart and the section you see that looks like a crack actually fell out in my hands, this is dangerous stuff.
I'm not sure BMW will see it the way you guys are, who are calling for a recall, but we will see.
I am just so thankful we saw this now and not 'after' the .......
I hope to have some more information on this tomorrow when i hear back from BMW.