Ned Snow, writing in the Syracuse Law Review (unfortunately unavailable at the Law Review's site), argues that Grokster makes Tivo liable for inducing infringement, because commercial-skipping undercuts the economic basis for commercial-supported TV. I told my copyright law students that there's no such thing as a natural right to a business model, but Congress can always provide.
I disagree vigorously with much of what Snow says; what I found downright puzzling was his claim that "In Sony, the claim of contributory infringement against the VCR manufacturer stemmed solely from the fact that the manufacturer sold VCRs; the manufacturer did not encourage VCR users to reproduce copyrighted broadcasts." Take a look at this ad, if the absurdity of Snow's claim isn't plain on its face.
Full cite: Ned Snow, The Tivo Question: Does Skipping Commercials Violate Copyright Law?, 56 Syr. L. Rev. 27 (2005).