The number of people who are willing to start something is MUCH smaller than the number of people willing to contribute once someone else starts something.

(2) to be unable to reciprocate

Collective action is the hardest kind of group effort, requiring a group of people to commit themselves to undertaking a particular effort together, and to do so in a way that makes the decision of the group binding on the individual members.

As the size of your network grows, your small-group pattern, where everyone connected to everyone, would first become impractical, then unbuildable. Let the small groups connect tightly, and then you connect the groups. But you can't really connect groups - you connect people within groups. Instead of one loose group of 25, you have 5 tight groups... See more

Imbalance drives large social systems rather than damaging them. Only 2% of users ever contribute, yet that is enough to create profound value for millions of users.

Famous means being the recipient of more attention than you can return in any medium.

The problem of getting the promise right is unlike traditional marketing, because most marketing involves selling something that will be made for the listeners rather than by them. ("Buy Cheesy Poofs" is a different message from "Join us and let's invent Cheesy Poofs together").

When a profession has been created as a result of some scarcity, as with librarians or TV programmers, the professionals are often the last ones to see it when that scarcity goes away. It's easier to understand that you face competition than obsolescence.

No effort at creating group value can be successful without some form of governance. People are basically good, when they are in circumstances that reward goodness while restraining impulses to defect.