As a practical matter, the business value really flattens and then drops as more sites are added.

Even the most modest intranet-to-Internet connections typically start out with firewall protection. Firewalls filter the traffic crossing the boundary, the simplest being a filter on IP addresses and TCP socket numbers to reject unwanted traffic. Many organizations pride themselves on funneling all traffic through a single firewall, which is often manually managed at central site for tracking web statistics. This limits security risks, as well as the number of firewall experts needed by the organization.

However, this approach does not scale, nor does it support the notion of extending the reach of the boundary.