How indie-microbusinesses and antibiotic resistant bacteria are surviving and thriving

Most people have a small number of people in their direct acquaintance but almost every pair of two random people can reach one-another via a handful of intermediary connections. Dunbar's number puts that degree of separation to six. Facebook recently said this number (the average 'degree of separation') is around 4, as calculated from the social-graph data of its more than a billion users.

Sociologists have found that people tend to gather in homophilous cliques (of size ~ 50 to 150) for maximal participation from members. When the group gets bigger, it breaks into two or more units. In this way, a small-world network emerges - with high level of clustering while at the same time the length of the path across the clusters is minimized. Most naturally emerging networks in the real-world like social networks are small-world networks(SFN).

• Scale-Free Network(SFN) looks like a corporate hierarchy- it has clustering but no redundancy in links (destruction of a single central node can separate the clusters)→ Efficient but fragile
• Random Network(RN) has lots of links means lots of redundancy - but no clustering, which leads to longer average-shortest-path between any two nodes → Robust but Inefficient
• Small-World Network(SWN) takes the best of both worlds - clustering and link-redundancy → Efficient and Robust

Edit(Nov 2nd, 2019):

In terms of the mobility-friendliness,

• Hierarchical scale-free networks as illustrated above have strong gatekeeping
• Random networks have negligible gatekeeping
• Small-world networks have porous gates.