In the 1940’s, the paleontologist von Koenigswald was searching for early human remains on Java and decided to enlist the help of the locals in his search by offering them “ten cents for every piece of hominid bone they could come up with.” Unfortunately for von Koenigswald (and for his findings), he discovered too late that the locals “had been enthusiastically smashing large pieces into small ones to maximize their income.”
From http://freakonomics.blogs.nytimes.com/2009/10/20/when-youre-...
(The story is from the book A Short History of Nearly Everything, which is one of the best books I've ever read. The amazing thing about the book is that it is in fact a short history of nearly everything.)
Combine the difficulty of getting incentives right with the inherent problems of Government and a dangerous mix results. For example, every time a subsidy is created, a special-interest group sprouts up dedicated to preserving the subsidy in perpetuity, long after it has outlived its utility.