In light of the recent Google Books/APA settlement, Harvard has examined the details and decided not to be part of the project after all.
Harvard’s university-library director, Robert C. Darnton, wrote in a letter to the library staff, “the settlement provides no assurance that the prices charged for access will be reasonable, especially since the subscription services will have no real competitors [and] the scope of access to the digitized books is in various ways both limited and uncertain.” He also expressed concern about the quality of the scanned books, which “in many cases will be missing photographs, illustrations, and other pictorial works, which will reduce their utility for research.”
Update: According to the comments, I had this sort of wrong. Harvard is deciding to not have Google scan their copyrighted books but the digitzation project proceeds apace. Thanks Jon.