Hierarchies: only a human artefact?

Most of the solution in SOA, like the cluster of UDDI registries, are based on an hierarchical structures because this is the way humans do in order to deal with complexity, i.e. in order to create comprehensible models.

But as a matter of fact, the reality is not hierarchical at all, this is the reason why information models becomes more and more unmanageable with the increase in complexity. Below a certain degree of complexity, the model can be oversimplified and a hierarchy represent a good approximation, but when complexity increases, it becomes impossible to stick to an hierarchy because reality is not as simple and it's based on different models and topologies, for example Scale Free Networks.