IANAL:<p>Be warned, although this may be morally justified, and very tempting, it may also be illegal. A similar situation might be that you could feel morally justified in putting a trap in your house while you are away, but it is illegal to do so.
Bill here - I wrote the article linked above and designed this kill switch.<p>It's been helpful to me several times when I've had trouble collecting from clients, but I only use it as a last resort. There's a pretty good comment thread on the post debating the ethics of the matter.<p>Also Acid_bath - I recognize what you're saying about validating over HTTP. It would not be acceptable for all my clients' sites to go down if my validation server goes down. That's why my code is configured to only disable a site if it is able to explicitly retrieve a KILL signal. No response from my server is interpreted as a lack of KILL signal, thus the site stays up.