[ryukafalz]

> Social network: you only engage on one if your friends/family/coworkers are on the same network.

This one isn't exactly based on fundamental economics given that federated social networks exist. Email has similar network effects and is not centralized.

[perlgeek]

None of the federated social networks seems to have reached the scale of the biggest centralized social networks.

Which leads me to believe that economics and incentives favor big, centralized social networks.

[toxik]

I think this argument could be made for many of these.