This is almost the worst thing that could happen for this thread...another bunch of pics of a failure with absolutely zero background information. Let the rampant speculation resume!
It's interesting that they're always on the right side. I bet the left side has more wall thickness because of the brake caliper mounting and the braking loads carried there.
It looks to me like the rider hit something and the fork broke at the weakest spot, which we all know and love. As others have said numerous times, it's unfortunate that the fork fails here when forced instead of degrading more gracefully, but I still think that's the nature of the old design vs. a manufacturing defect. I'm not calling it a design "flaw" either -- everything will fail somewhere when prompted to, and these forks seem to do it at the RH axle boss instead of somewhere else. BMW realized this was not optimal and reinforced the area on later forks.
That still doesn't explain the OP's failure, but neither does anything else. I doubt we'll ever know. My problem is that I enjoy my G so much I apparently don't care. I did tell my wife that if I mysteriously stack it to make sure the front fork is scrutinized, and she's got the bookmark to this thread.
If it happens to me and I live I promise you I'll get a message through somehow, black helicopters be damned! My dying wish will be to see this thread closed once and for all.
Oh, and that eBay listing makes me feel good about my resale value.