Many physicists, mathematicians and computer scientists use arXiv and as Paul Ginsparg articulates in his comments about scooping, it is not plausible to claim that “I never saw it.” Preprints are undergoing a transition in some fields of biology where the numbers are still small and many scientists do not know about them. This situation will likely change in the future as they are integrated into more search tools and become more  discoverable. However, even now, preprints are permanent public documents with DOI. They are a record of an accomplishment that can be pointed out to any other scientists, cited in journals, and in funder applications and reports