Apple’s Social Network
https://www.howtogeek.com/252100/what-to-do-if-you-cant-receive-text-messages-from-iphone-users/
The article talks about rigorous steps Apple sends customers through when they change to an android or non-Apple phone. Apple uses iMessage, their proprietary messaging platform, to allow customers to freely send message to one another. Apple also uses iMessage to send text messages when someone in the chat doesn’t use an Apple product. The two message types are distinguished by the blue bubble for iMessages and the green bubble for a text message, but how does Apple know who uses one of their devices or a competitors. Apple maintains a database of all phone number associated with an Apple device so when someone attempts to send a text to a phone number they can determine whether to switch from the default blue bubble to the green bubble.
Here Apple takes advantage of the structure of social networks and the position of Apple users within them to incentivize more people to use Apple products. If two people in a three person group chat are using Apple devices, social pressures incentivize the third person to switch to an Apple device so that all messages within the group would be free. This also relates to cascading since more people using iMessage over text messages will compound the social pressure to move to an Apple device.