When a blogger asks "What 3 Industries Is The Apple iPad Threatening To Decimate?" he's using the word in its popular sense, "destroy."
Originally, decimate meant something brutally specific.
In ancient Rome, military leaders reacted swiftly to rumors of mutiny. They randomly selected one-tenth of the men in a mutinous unit and killed them.
That practice was known as decimatus, after decem, the Latin word for ten.