I don't think Napster really expected that to be taken so literally; Metallica hired a consulting firm, which proceeded to identify 335,435 Napster users that were illegally sharing Metallica songs. On Wednesday, Lars Ulrich himself (one of the members of Metallica, see this ZDNet story) will be delivering 60,000 pages of information on the 1.4 million violations.
My understanding is that new Napster ID's can be registered anonymously and practically at will, so I doubt this move will really slow down anybody whose user ID gets banned. I see this more as Metallica peeing on Napster's head. Just imagine trying to cull over 335,000 user ID's from 60,000 pages of printed text; I'm betting the records are irregular enough that attempting to use optical character recognition software and pull the ID's out won't work.
Could Metallica give Napster an electronic copy of the information to make things easier? Sure, but couldn't you see them giving Napster 60,000 pieces of paper just for the PITA factor? I could.