Newfangled spam zombies read your past email, imitate your style:

When a computer is turned into a spam zombie, it will first be mined of its address book, mail client configuration, and mail archives. Then the spam program will use Natural Language Processing techniques to send spam messages to the victim’s contacts that look a lot like messages that the user has previously sent.
[SlashDot]

Such are the monsters of our cleverness. Beware, Daedalus!