Take a look at this useful brief history of the NAST project. It is clear that ASERL (Association of Southeastern Research Libraries), in an initiative led by Paul Gherman (Vanderbilt), and Paul Willis (University of Kentucky) began grappling with these issues back in 1999. Significant data comparisons were done in 2003 and 2004, accompanied by early discussions of "shared virtual storage" and related strategies. ASERL, OCLC Research, and RLG all played major roles in this important work. Policy frameworks and data requirements for large-scale shared print were developed and reported in 2007. This groundwork continues to benefit all of us now working in this space.
Interestingly, meetings tied to ALA conferences were also occurring around this work, and in many ways these are the real antecedents to PAN. Among the invitees in a December 2006 email are some of the same people who continue to make major contributions to shared print efforts today: