This is interesting… and it ties in with a great talk I heard once about Thylacine sightings in Tasmania .. of which there are many.
Reliance On Unverifiable Observations Hinders Successful Conservation Of Wildlife Species (June 24, 2008) — Researchers from the US Forest Service’s Pacific Northwest and Rocky Mountain Research Stations examined three cases of biological misunderstandings in which unverifiable, anecdotal observations were accepted as empirical evidence. Ultimately, they found that this acceptance adversely affected conservation goals for the fisher in the Pacific states, the wolverine in California, and the ivory-billed woodpecker in the southeast by vastly overestimating their range and abundance. The researchers’ findings appear in the current issue of the journal BioScience. … > full story