Jonah Lehrer blogs here about why people are turned off by having too many choices, with reference to work by Sheena Iyengar.
I once heard a man at a science fiction conference say that, back when he started reading science fiction -- maybe in the 1940s or so -- a person could say to another person, “I like science fiction,” and get the reply, “I like science fiction too,” and those two people would know they were talking about the same books. But eventually that ceased to be true: it reached the point that two voracious science fiction readers might easily not have read any of the same authors. There should be a term for the moment in the history of a literary movement when this threshold is crossed...
Samuel R. Delany, in the introduction to his essay collection About Writing, uses the example of Romantic poetry in English -- "Though it may take a decade or more of reading, a single reader can be familiar with the totality of that field." Delany makes a persuasive case that there are exponentially more major poets writing in English today than there were in 1814 -- we should expect this, given that there are exponentially more people now who can read and write English than there were then -- and that it's therefore impossible now for anyone to have read all the major poets writing in English today. Delany concludes, "Thus, the doling out by the literate readership of fame, merit, or even simple attention is an entirely different process from what it once was."
Iyengar's work suggests that, when there are this many choices, consumers stop behaving rationally. Making a rational choice simply becomes too time-consuming. If there are too many good books to read already, that creates a dilemma for those of us whose life's ambition is to write more good books -- to the extent that we succeed in our ambition, we're only making this particular problem worse.