Seth Godin has a useful post on how to make a million, or perhaps how not to. Godin points out that one popular strategy is to try and make $1 from each of a million people, or even £0.10 from 10 million people. However, he points out, this usually fails. Where people go wrong is not in their evaluation of whether their product is good enough to generate a margin of $1 or even $0.10. The problem tends to be in reaching that many customers.
In market research the problem is worse. Where we are using human skill and intelligence there is no long tail, most of the money comes from the few large clients, as does most of the risk!