[brlewis]

I am not affiliated with Facebook myself; I barely use it, but given how big it is I bet they do user studies in addition to metrics collection. Metrics alone leave out important parts of the human element, but user studies alone are a biased sample.

[rohit2412]

Given the speed and comfort of not doing user studies, I expect "move fast and break things" Facebook to not care about user studies at all

[jartelt]

I know several UX researchers at facebook. Yes, they do in person user studies.