The primary precedent for this case was the Court's famous 1984 decsion ruling that Sony's Betamax VCRs did not facilitate copyright infringement because the products were "capable of substantial noninfringing uses." Grokster and StreamCast successfully persuaded lower federal courts that an analogy existed for P2P software, but the Supreme Court didn't buy it.

Again, the essential element in the Grokster decision is that there was enough evidence that Grokster and StreamCast were actively "promoting" their software to be used for infringement purposes in marketing campaigns. In Justice Souter's words, "One who distributes a device with the object of promoting its use to infringe copyright, as shown by clear expression or other affirmative steps taken to foster infringement, is liable for the resulting acts of infringement by third parties."

This "inducement" theory reasoning leaves open the door for other P2P networks to successfully argue that, like VCRs, they are capable of "substantial noninfringing uses" and, unlike Grokster and StreamCast, are not promoting illegal use. In concurring opinions Justices Breyer, Stevens and O'Connor seem to suggest that such use would be acceptable. But in a counterveiling concurrence Justices Ginsburg, Rehnquist, and Kennedy suggested that the noninfringing uses must be "commercially significant."

So the Supreme Court remains divided and unclear over what constitutes a "substantial noninfringing use." Writing in Salon, Siva Vaidhyanathan argues that with over 100 million working copies of P2P interface software, Grokster will do nothing to stop it, but it can still chill innovation:

This is why courts and legislatures should be very careful when regulating technological innovation and copyright: Broad rules and legal uncertainty can put a chill on, or even wipe out, really useful and important developments.

As Jim instructed Huckleberry Finn when Huck claimed Solomon was the wisest man who ever lived: "De 'spute warn't 'bout a half a chile, de 'spute was 'bout a whole chile; en de man dat think he kin settle a 'spute 'bout a whole chile wid a half a chile doan' know enough to come in out'n de rain."