Essay Question vs. Multiple Choice
Big data gives you answers like multiple-choice exams test knowledge. It's a terribly constrained way to evaluate single points of interest. They tell you nothing that is not specifically asked for in the exam. They're easy to feed into databases, easy to run comparative queries, and give an illusion of being simple and effective.
Essay questions generate non-standard answers, and are difficult to shove into databases. Much harder to evaluate and sort/compare/etc. However, they give a TRUE picture, since the respondent can include anything in their answers the tester might not have asked about.
Big Data: easy to work with, terrible picture of reality.
Anecdotes aren't always bad, folks. "Goat weed cured my cancer!" is bad anecdotal evidence for goat weed. "Big Box Electronics fixed my computer in an hour after Nerd Squad failed! Happy customer!" is a good datum point for customer service. Much better than a stupid survey saying "rate your satisfaction from 1 to 5".