"The Engagement Effect" is what happens when a product gets stickier, and more engaging, as more users join. This is the closest to the classic definition of the network effect, as defined by Theodore Vail of AT&T. However, I'll describe it in modern terminology, using the language of retention curves and engagement metrics that we use in dissecting the performance of new apps.

No one wants to live in a ghost town. No one wants to join an empty community In the early days, it was our job each day is make sure there was good content on the front page. We'd past it ourselves, using dozens of dummy accounts. Otherwise the comma mity might dry up.

The older dating sites made it feel like you were doing work, like you were inside the office, You'd go and do work emails during the day, then go home and write more messages at night. Only to prospective dates rather than work colleagues. Tinder was different - it mule dating fun. You could sign up without filling in a bunch of forms. It's visual, you just swipe back and forth, and you could take foe minutes to do it while you were waiting in line or something like that. I's a form of entertainment.

The hardest problem to solve in creating the first atomic network is, well, attracting the hard side. Focus on attracting content creators to a new video platform, or sellers to a new marketplace, or the project managers inside a company to a new workplace app. The other side uf the network will follow.

Disruptive technologies are dismissed as toys because when they are first launched they "undershoot" user needs. The first telephone could only carry voices a mile or two. The leading telco of the time, Western Union, passed on acquiring the phone because they didnt see how it could possibly be useful to businesses and railroads-their primary customers. What they failed to anticipate was how rapidly telephone technology and infrastructure would improve (technology adoption is usually non-linear due to so-called comple. mentary network effects). The same was true of how mainframe companies viewed the PC (microcomputer), and how modern telecom companies viewed Skype. The next big thing will start out looking like it's for a niche net

The solution to the Cold Start Problem starts by understanding how to add a small group of the right people, at the same time, us-ling the product in the right way. Getting this initial network off the ground is the key, and the key is the "atomic network"_ the smallest, stable network from which all other networks can be built.