Sorry, you need an invite to sign up to this app.” No one will be happy to see a message like this. It might seem like a counterintuitive way to launch an app, particularly during the Cold Start phase, when new users are so desperately needed. Why turn down users who want to try your product? Yet this constraint is at the heart of the so called “invite-only” strategy for launching a product. And for Gmail, LinkedIn, Facebook, and many other networked products, it has worked. Why?
