Ahhh, I just came from the Vodaphone comments, and my context switching is slow.
It's true that the legal side is onerous. We like to think that it prevents more trouble than it causes, but reasonable minds may differ.
I still think my question is an interesting one, even if it's not what you were saying. I don't know that there's any public precedent on the matter, but I imagine it's not as rare as one might think given all the different sort of public and private NDAs that exist.
Based on my experience of it, negotiation took a couple weeks, and warrants/reps took sixteen thousand years. My partners went into the process looking like young David Lo Pan, and ended it looking like old David Lo Pan. (I spent the whole process as the weird floating orb of goo with the big eyeball).