"As Paul Buchheit, creator of Gmail and partner at Y Combinator, says, the correct order of operations is to “sell before you build.” When you launch, you want a whole list of people that you can tell to buy it. But more than that, you want to ensure that you’re investing all that time building something that people want to buy."
As far as I can tell, they built a product for 40,000 people over a certain period of time without generating a cent in profit or knowing in advance that any of those people would ever consider paying from the product. While some users did claim they wanted a team version they would pay for, this was only after the base product was built without knowing people would pay for it.
This bugs me a bit because I'm working on a project where I'd love to be able to sell before I build, as it's obviously a very sound principle, but in practice I just can't see how to go about it and I was hoping to learn something new from this post.