bowWave - I interpret it to mean that these domains work like partitions do on a server, in that they seperate various sections of the server to specific users. In doing so, they can allow their policy or identity management policies and standards to be either applied to a specific domain (seperately), or holistically across domains.
This allows policy, standards, and identity management to be maintained outside of the individual domain's application code, in a middleware-like set of domain independent business rules. IMO - policy/identity management is the perfect place for useful stage web-services to emerge.
t123