Therac is the first one I list and Knight Capital is the second. It is in fact possible to bankrupt your company by misusing feature toggles.
Some years later, I interviewed at Knight Capital, just a couple of weeks before their blowup. (Dreadful interview at which I did dreadfully, being asked to write C _over the phone_ by a supremely uninterested engineer. Quite a red flag in retrospect.)
No pun intended?