One of my fascinations is with cryptozoology. When researchers pursue "cryptids," as the uncaught or unclassified are called, an interesting question arises: when you declare victory? When is an animal "discovered?"
I had an interesting exchange on this with anthroplogist/cryptozoologist Dale Drinnon, who thinks me something of an idealist about the way science works. Admitting that that is true, here are my thoughts.
It's easy to say that a certain cryptid has been discovered - to our satisfaction - and thus is no longer a cryptid. But saying it has no impact on science or conservation, and thus does not accomplish anything concrete.
While some zoological scientists may be too restrictive in what they accept, there is at least a standard for formal discovery and acceptance - a holotype available for physical examination and a paper published in a refereed journal. Granted, the zillions of tropical insects, etc. don't all get papers on them specifically, but the significantly-sized animals usually put on crytpid lists would all rate publications. And the insects and spiders and so forth at least turn up on the databases kept by the IUCN, the USFWS, etc., providing "evidence of acceptance."
Photographs or seafloor trackways have on occasion gained some acceptance as type specimens, but not in any of the controversial cases cryptozoologists spend most of their efforts on.
Without that standard, anyone can declare, say, the yeti discovered to their satisfaction, based on reports and sometimes hard evidence that, for whatever reason, is difficult to access. The trouble is that everyone's opinion is essentially equal, and there's no meaningful impact on science, conservation, etc. made by declaring a species discovered. (There would be if, say, George Schaller said it, but cases where a widely recognized authority endorses a cryptid as discovered (not just deserving of investigation, ut discovered) are rare indeed.)
Even having a scientific credential does not mean one's opinion has any measurable impact - Jeff Meldrum's endorsement of sasquatch, for example, has not led to funding for sasquatch investigation and conservation, has not gotten the animal in textbooks, etc.
My own inclination is to declare an animal "discovered" only when the two-pronged standard of an available holotype (at least in the form of a DNA sample) and peer-reviewed publication is met. Those standards are not magically correct, and may overlook some valid species, but they are the closest thing there is to a formal standard accepted worldwide.
And that, of course, is just one person's opinion.