I suspect that intra network latency has a significant impact on intelligent systems. Interconnectivity also seems crucial but as you add nodes the number of connections needed to keep that closeness in the networks scales dramatically. These connections also need space so if you keep the same level of interconnection as you add more nodes, your density drops and so your latency goes up.

There is thus a fundamental tradeoff between network size, network latency, and network interconnectivity that can't be avoided. While we may eventually beat the human brain on some or all of these measures, there is good reason to believe there are fundamental limits on the scalability of intelligence.