Came here to say this. Ten years later, there are many more entrepreneurs who think about revenue (and even profitability!), not just sending their user numbers to the moon.

Presumably the first thousand users will help you to figure out what are the most important aspects of your product/service, what you can charge for, what you should give away for free, etc.

It would be really interesting to see a follow-on article titled How To Get Your First 1,000 Customers.