What is the most-radical example of a disrupting service / model in the accounting business services industry.
What I mean by disrupted is that someone has at some point taken such a radically different approach, to deliver the same service that the old way of doing things was abandoned.
One comparable example (though not a business service):
The invention of the electric light bulb. This was a technology, which completely disrupted the lighting market. However, I assume that if Thomas Edison would have walked around from house to house to and attempted selling a light-bulb together with some sort of membership in the local grid, then his marketing efforts would have failed because they would not have believed that it was possible. His advantage was that he could show people that it worked and thereby immediately gaining trust.
Was there any time in U.S. history in which accounting/finance/banking took a sharp turn? Did this occur, for instance, during or as a result of the Great Depression? Was the collapse of the "Big Eight" accounting firms into the "Big Four" following the demise of Arthur Andersen such a watershed event?