This post details how Buffer used their landing page to lean startup style validation of their product before they built anything.
The aim of this three-page MVP was to check whether people would even consider using the app.
They also validated whether people were comfortable with paying for such a product.
The result of this experiment was that people were clicking through and giving them their email and a small number of people were clicking on paid plans. After this, they didn’t hesitate to start building the first minimal version of the real, functioning product.