Duds are hardware that goes bad, like a disk drive, network adapter, NAS, or server. There are an infinite number of ways and combinations things can break in a moderate sized IT shop. How much money / effort are you willing to spend to make sure your weekend isn't ruined by a failed drive?
Floods are catastrophic events, not limited to acts of God. Your datacenter goes bankrupt and drops offline, not letting you access your servers. Fire sprinklers go off in your server room. Do you have a recent copy of your data somewhere else?
Bud is an accident-prone user. He accidentally deleted some files... the accounting files... three weeks ago. Or he downloaded a virus which has slowly been corrupting files on the fileserver. Or Bud's a sysadmin who ran a script meant for the dev server on the production database. How can we get that data back in place quickly before the yelling and firing begins?
There are more possible scenarios (hackers, thieves, auditors, the FBI), but if you're thinking about Dud, Flood, & Bud, you're in better shape than most people are.