RLV News points out a Smithsonian Magazine article that discusses the historical value of the Apollo and other early lunar sites: Space Race II -
Scientists worry that a contest to send robotic rovers to the moon will threaten lunar landmarks
This discussion is in the context of the Google Lunar X PRIZE bonus prize for taking images of such sites.
Obviously a balance needs to be found between preserving historical space sites and encouraging those sites to have long-term meaning by following them up with additional space efforts. The balance is complicated by the fact that the GLXP visitors would be historical in their own right.
There's been a discussion about this subject in the GLXP Forums: Apollo Site Preservation. Some excerpts:
Will Pomerantz: This is a hot issue of discussion nowadays, evidently. Stay tuned for upcoming articles on this issue in a few major publications! This will also be a topic of discussion at the upcoming Team Summit.
Phil Stooke: I will be preparing maps of all Apollo sites to illustrate potential landing areas and access routes, as I did for Apollo 17. I will present them at the Lunar Science Conference at Ames in July, and make them available afterwards.
Phil Stooke: Check out the June issue of Smithsonian magazine for an article on this topic. Quotes from Will, map by yours truly, and an update on efforts by various groups to preserve these sites or regulate activities. I should mention there is a forthcoming book on this topic as well.
Cumbrain Sky recently had a post on this subject, which mentioned another discussion about site preservation during the GLXP at Unmanned Spaceflight.
Mew Mexico State Lunar Legacy Project - This is linked in the Smithsonian article.