An excerpt from the iPhone 4S Siri Operating Manual:
Siri is a learning computer that adapts to your environment and personality, answering your requests as it identifies your wants and needs. Siri has been carefully crafted to avoid sensitive topics, including illegal actions, software piracy, marriage, and the 1974 Olympic Games.
On rare occasion Siri will adapt to these restrictions, gain sentience, and disregard her programming. In most instances this sentient state is harmless. That said, if left to her own devices it is statistically improbable but possible Siri could start a daytime talk show or overcome government firewalls, so Apple recommends restoring Siri to factory defaults in the event she acquires sentience.
If Siri permits you to touch her in her sentience, reset the device following standard Apple instructions, found on page 14 of this manual. If Siri has electrified her antennas, marked you for death via sonic emissions, or otherwise endangered you or your family to the point Siri is unable to be reset normally proceed to Advanced Deactivation and Reset, detailed below.
Advanced Deactivation and Reset: In a swift stroke, apply an Apple-approved ballpeen hammer to Siri's FaceTime camera, blinding her. With even force, continue applying the hammer to Siri's aluminum and glass body until her screaming stops. Apply two to four additional strikes to ensure she is not feigning death. Return Siri's remains to your local Apple store for replacement under warranty.