Four Viral Loop Drivers [updated]

I was noodling about different categories of viral loops and started making a list...

Viral Loops typically center on:

1. Contact Lists -- e.g., inviting new people thru the process of finding/adding new contacts to a contact list


2. Conversations -- e.g., inviting new people by adding them to chats, events, groups, etc.


3. Media -- e.g., inviting new people by sharing media/content with them


4. Incentives -- e.g., inviting new people to unlock functional or financial incentives

Any others that you can think of?