Various other forums. I've been following a few threads on the subject. Most that attempt delidding know the risks and can afford a replacement. As such they tend to just report their failure inside the thread rather than make a song and dance about it, like the handful of "woe is me" threads
I'd estimate at least a 1 in 5 failure rate. High enough for me not to try anyway.
I have only read of one person damaging their 3570k when delidding.
Still there are risks involved but if you are handy and take your time, as well as heating up the chip in the oven first, it is easy enough to remove.
Of course warranty is then gone and maybe the resale value compromised but I have never had a chip fail on me yet where I have needed the warranty