Last year, a potential client approached me to perform research in a nearby county on an ancestral family. This client had never performed research before, instead relying on the work of others, but was interested in moving this particular family back in time a generation. After consulting with me and the others who had performed previous research, the client decided not to hire me because all the records had already been searched. The belief was, amongst that group, that there was no further information to be found pertinent to that family or the research problem because they had already gathered all documents created by or for the ancestor in question.
I strongly disagreed and explained why, but still lost a client over a common misconception, that all there is to research is extracting information from records about a particular ancestor.