Define validate. That is kind of the crux of my question. If it means "profitability" then that is a different threshold than "users." I am trying to figure out what PG is trying to describe.
It's pretty obvious when it happens but it's most definitely not profitability. Rapidly growing usage (ie, traction) with an envisionable business model is usually sufficient. While the revenues themselves are not strictly necessary, it does help to demonstrate the ability to collect them.
