Small world networks have the advantage of being able to find data in log N time where N is the network size, they're also completely decentralized, self-healing, and distribute load evenly across peers. The principle is similar to DHTs like Kademlia but more flexible and intuitive IMO, while having similar scaling characteristics.
It's surprisingly common for people to confuse small world networks with "scale free networks", but scale free networks rely on a subset of highly connected peers which do a disproportionate amount of the work - which isn't truly decentralized.
The new Freenet design incorporates adaptive learning into the routing algorithm. When a peer is deciding where to route a message, it predicts the response probability and time for each neighboring peer based on past performance and chooses the best. With conventional "greedy routing", peers choose the neighbor with a location closest to the data being retrieved. The new approach is adaptive to actual network performance.
[1] Both the original Freenet from 1999 and the new sequel we're currently building - see https://freenet.org/ for more. We hope to launch the network in the next few weeks.