Steven Johnson has a great passage on the contribution of the amateur in The Ghost Map story (see below).
This is a theme that resonates. In The Long Tail, Chris Anderson makes the case for amateurs in astronomy. (Is it he, who points out that the root of the word "amateur" is to love?)
Stigler had an important early paper in which he discusses the professionalization of the economics profession. He praises the results, but what he presents provides some grist for the mill of criticism too. For example, the exit of the amateurs, reduced the applicability of the work, and turned research more toward internal puzzle-solving, and model-building.
The web is a leveler in science, as suggested in an NBER paper. Maybe the result will be a resurgence of amateurism, and maybe that won’t be all bad.
(p. 202) But Broad Street should be understood not just as the triumph of rogue science, but also, and just as important, as the triumph of a certain mode of engaged amateurism. Snow himself was a kind of amateur. He had no institutional role where cholera was concerned; his interest in the disease was closer to a hobby than a true vocation. But Whitehead was an amateur par excellence. He had no medical training, no background in public health. His only credentials for solving the mystery behind London’s most devastating outbreak of disease were his open and probing mind and his intimate knowledge of the community.
Johnson, Steven. The Ghost Map: The Story of London’s Most Terrifying Epidemic – and How It Changed Science, Cities, and the Modern World. New York: Riverhead Books, 2006.
(Note: A probably relevant, much praised book, that I have never gotten around to reading, is Martin J.S. Rudwick’s The Great Devonian Controversy: The Shaping of Scientific Knowledge among Gentlemanly Specialists.)