A dangerous phenomenon: sub-network metastasis.

This happens when a sub-component of a network grows much faster than other parts of the network.

It then grows to overshadow and encircle the rest of the network, choking it out and limiting its size.

The system now is captured by this sub-network, becoming ever more optimized for the sub-network, and ever worse for the rest of the network.

For example, Orkut was captured by the growth in Brazil, making it a less good fit everywhere else.

As another example, OnlyFans was captured by porn; now the "polite" use cases are crowded out.

The web's early PMF was also about porn… but none of the front doors mentioned that and so it was possible for the polite parts of the network to also grow without being crowded out.