[WhitneyLand]

Look at it from reverse - of all the big/successful startups out there how many used any formality or rigor in validating their ideas?

Even if they did validate early on what made them successful often changed drastically based on what was known when the company was started.

In otherwords, what percentage of the time does this payoff?

[w1ntermute]

Out of the four $10b+ companies founded since 2007, Dropbox and Airbnb definitely used Lean techniques[0], and Uber probably did[1]. That only leaves WhatsApp, which there isn't much information about out there. But considering how little funding they took, it's safe to assume that they utilized similar techniques.

0: http://www.hult.edu/en/news/hult-labs/2013/august/the-lean-s...

1: http://www.quora.com/Lean-Startups/Did-Uber-use-any-lean-sta...