In an analogy to the "Windows Genuine Advantage" program, Simon Phipps mentioned
the recent discovery of explosives underneath a British airfield, and draws an analogy to anti-piracy "kill switches" embedded in software.
While not directly analagous to a "kill switch", a couple years ago I heard of a somewhat more astonishing case of leftover lurking horrors: in 1993, World War I-era mustard gas shells were
in what is now an affluent residential neighborhood of Washington, DC in 1993. As of this summer, the
was still in progress.
Returning to the real target : I share Tim Bray's concerns. License enforcement by intentional denial of service has no business going into mission-critical software; we have a hard enough time coping with denial of service from unintentionally introduced "features".