It's harder than you are suggesting to find a leading indicator of future engagement. You want to find a metric that is relatively foundational, and is going to produce engagement across a variety of dimensions later on (visit frequency, tendency to pay, tendency to add content, tendency to invite others etc).

For instance, when signing up to Facebook, there is a bunch of stuff they want you to do: add friends, invite people, add content like photos, and come back on day 1, day 2, and so on. It turns out that it's the first activity that is more predictive of future engagement than the others, and specifically 7 friends in 10 days is an important threshold. You can't figure that out from your intuition alone, and you definitely can't get the values of # of friends in # of days just by consulting your intuition, or your sense of what's obvious.

At the same time Chamath from Facebook was keen to point out that there was nothing mystical about what the growth team at Facebook did. He said the best way of describing what they did on the growth team is that they:

- Measured things

- Tested things

- Tried things

His main take-away was that one should be extremely rigorous and analytical when thinking about what drives engagement, and not rely on your gut, or company lore.