"Obviously, if you understood a business perfectly — the future of a business — you would need very little in the way of a margin of safety. So the more volatile the business is — or possibility is — but assuming you still want invest in it, the larger the margin of safety... Well, if you’re driving a truck across a bridge that holds — it says it holds 10,000 pounds — and you’ve got a 9,800 pound vehicle, you know, if the bridge is about six inches above the crevice that it covers, you may feel OK. But if it’s, you know, over the Grand Canyon, you may feel you want a little larger margin of safety, in terms of only driving a 4,000 pound truck, or something, across. So it depends on the nature of the underlying risk."

- Warren Buffett -