"It is very difficult for a set of metrics to fully measure what you value."

This talk from Adam Mosseri about being data informed is great. It is worth the thirty minutes. At 13:00 in he says the line that makes this post's title. He then shows two examples from Facebook where the data sent them in wrong directions. These are my summaries of the reasons:

  1. Most of your data is generated by your power users, so if you aim for increasing pure engagement you will market to this group only.
  2. When you optimize for one piece of data you will eventually ignore anything that is not measured by the data.

I think that both of these points contain great truths for teaching.

Bonus quote, "The greatest risk is taking no risk at all." (29:20)

UPDATE: Forgot the link.