Why Facebook should hire astronomers

Much research in corpus linguistics or computational linguistics occurs on data that naturally occurred. It's part of the traditions in psychology to manipulate your subjects because that's the only way you can get more direct observation of suspected cause/effect relations, especially when those are subtle enough to go under in the noise in "in the wild" data.

Given a big enough sample size and a multi-factorial model (i.e. a model that models all confounding factors as well as the variable you're interested in), the importance of manipulation should decrease, and many astronomers, economists, or computational linguists would be able to draw meaningful inferences in such a study. Psychologists may have gotten too used to the idea of "get experimental subjects, present with manipulated input, do comparison statistics" to consider a purely observational study as the default.

tl;dr: It's not just astronomers, many fields do empirical studies without manipulating their subjects in a Skinner-ian fashion.