See this 2004 Boston Globe op-ed piece in which Palfrey argues that purveyors of p2p software including Grokster should not be held liable for their users' infringements (a position subsequently rejected by the Supreme Court).
UPDATE: In his 2008 book Born Digital: Understanding the First Generation of Digital Natives, Palfrey again makes clear that use of p2p networks to download and "share" music constitutes copyright infringement:
Use of Napster to download songs was "breaking the law" (p. 133)Palfrey argues persuasively that file-sharing is popular, and makes clear his disagreement with the record labels' suits against individuals. But he forthrightly, and repeatedly, acknowledges that the use of p2p systems to obtain music without permission is blatantly illegal. If he indeed testifies at trial, cross-examination should be very interesting.
"In a legal sense, anyone who uploads music on P2P networks is violating the intellectual property of the artists, whose interests are formally protected by the laws of virtually every nation in the world." (p.133)
On Napster: "there was little doubt that the file sharing itself was illegal..." (p. 134)
Napster was "well-known for large-scale copyright infringement" (p. 135)
On the record labels' individual suits: "most [defendants] are indeed liable for the infringement" (p. 141)
'[W]e believe that it is important to uphold the rule of law, not to ignore rules that seem merely inconvenient.... " (p. 142)
"Take note: Online file-sharing of copyrighted works is illegal in the United States and in most other jurisdictions in the world." (p. 142)
"people who are sharing thousands of songs for free when they ought to be paying for them" (p. 150)