It's the sudden unexpected market turn: Your company's software is hacked. The perfume you were selling is found to cause rectal bleeding. (And yes, it's a boon for your competitors' anti-rectal-bleeding drug division but that doesn't help YOU.) It's the death of your beloved CEO at only 42 years old, taking with it the secret sauce recipe of the company. It's an asteroid hitting the earth...only landing on YOUR building, wreaking havoc on your business and, well, on you (especially if you were in the building). You know: bad, out of outer space, liable to leave a big steaming crater where your business once stood. See ACT OF GOD.
