Do You Really Want to Know?
HP Lovecraft's short story "The Call of Cthulhu" opens with a fascinating epigraph:
The most merciful thing in the world, I think, is the inability of the human mind to correlate all its contents. We live on a placid island of ignorance in the midst of black seas of infinity, and it was not meant that we should voyage far. The sciences, each straining in its own direction, have hitherto harmed us little; but some day the piecing together of dissociated knowledge will open up such terrifying vistas of reality, and of our frightful position therein, that we shall either go mad from the revelation or flee from the deadly light into the peace and safety of a new dark age.
Lovecraft was of course referring to putting together the pieces of evidence that lead to the discovery that we share the universe with horrible cosmic entities of vast intellect and profound indifference toward human life.
However, it seems that putting together more knowledge isn't always good on a merely human scale either, and sometimes it would be best to leave those pieces apart. In particular, there is the risk that Big Data can destroy our ability to remain ignorant of information we'd rather not know. Random bits of publicly known information, all brought together by a machine, can add up to a profound breach of privacy. Or, less sinister but still damaging to our happiness, it can destroy surprises we'd prefer to wait to have revealed until a significant milestone moment.