Careless users do. Over at Denise Howell's always-entertaining Bag & Baggage blawg, she makes the following priceless observation:
Craig posits a defense [to a lawsuit accusing Microsoft of unfair business practices for failing to secure its software against viruses] that would liken software to firearms, which is both insightful and, in my twisted little brain, funny. (I can just see the t-shirt: Windows Doesn't Kill People, 2600 K1Ll5 p30PlE.)
California's Legal Swiss Army Knife Sprouts A New Blade, Takes A Swipe At Microsoft (03 Oct 03) (link omitted). This, combined with a not-entirely unexpected item from Kelly Talcott's Infringing Actions noting that (gasp! shock! horror!) some P2P software contains malware—bringing to mind the aphorism concerning honor among thieves—actually highlights a problem with binary logic more than anything else.
Our legal system has only two verdicts: guilty or not guilty (or, on the civil side, liable or not liable). As any prosecutor, plaintiff's attorney, or investigator knows, this makes dealing with instances of shared responsibility especially difficult. By its nature, the legal system reduces a complex web of interrelationships to the single question of whether one particular set of actors in those interrelationships is responsible for the harms that have befallen another. The "guns don't kill people, people kill people" argument advanced by the gun industry is an excellent example. Under that reasoning, the fact that a tool has a conceivable legitimate use means that the toolmaker is completely absolved of responsibility for misuses. Cf. Sony v. Universal Pictures, 464 U.S. 417 (1984) (because VCRs may be used for the fair-use activity of "time shifting" TV programs, they are not unlawful devices that inherently infringe copyright).
Consider, however, the instance of the "Saturday Night Special." Sure, someone could buy a Saturday Night Special with the avowed purpose of legal target shooting. (Whether a trained rangemaster would even allow such a nutcase onto a target range is beside the point under this argument.) Wink wink nudge nudge. It is undeniable, however, that the principle—and perhaps only conceivable—purpose of the Saturday Night Special was the unlawful killing of people. Self-defense is a justification that prevents or mitigates assignment of blame; it does not make the killing itself lawful. Conversely, however, a trained combat firearms instructor will laugh at someone who shows up for combat training carrying a brand-spanking-new shotgun loaded with birdshot; in theory, and perhaps sometimes even in practice, such a weapon could be used to kill people, but it is optimized for killing pheasants. The gun industry seizes upon the latter weapon, arguing that its characteristics swallow the characteristics of firearms that are optimized for killing people; gun prohibitionists do the reverse.
This is exactly what chapter 12 of the Copyright Act does with "copyright circumvention devices." Frankly, this part of the DMCA is largely indefensible. Cf. Bernstein v. Dept. of Justice, aff'd en banc. Under the reasoning of Sony, since DeCSS does have the lawful use of allowing consumers to play DVDs on Linux machines—which, unlike Windows and Macintosh machines, ordinarily do not have drivers available to play CSS-encrypted disks—reinforced by the reasoning in Bernstein as to publishing specifications for cryptosystems, this part of the DMCA cannot stand. What the courts have instead done is rewrite Sony, which admittedly is an extremely poorly written and obtuse opinion, to require that a device or system have not just any, but some significant lawful purpose. This explains why Napster could, in the face of Sony and Bernstein, hold that Napster's system was unlawful. Although there was a legitimate use offered—recipe sharing—the evidence established that Napster was overwhelmingly used for an unlawful purpose.
Perhaps, then, what this all means is that "software doesn't infringe copyrights; copynorms infringe copyrights." Or perhaps it is just a monument to the difficulties with inductive reasoning and unconsidered cases.