Keith Rabois explains that the key to LinkedIn’s success was investing 80% of resources in virality

I spent almost three years at LinkedIn 2.8 years and I started as employee number 20 and when I left two and a half years later we were at employee 59. People forget that like it took two years to get to a million users which in a social product feels like an eternity. Revenue had like none for the first two to three years. In fact, when we hit a million dollars of revenue it was like cause for epic celebration. The key was Reid hoffman who founded LinkedIn was very savvy and he knew what the ingredients for success were. He was very consciously aware that link how to be a viral product we could not afford to pay for customer acquisition. So almost everything was predicated on how do you create a true viral product and there's ways of measuring it, et cetera. And that was like 80% of the resources. And once we nailed the viral product and the coefficient was above 1, then we could take time to build other products.