http://www.obscuritus.ca/Technology/Federated_vs_Global.html

This is worth a read. This person has spent some time thinking about these issues. I'm not saying his/her conclusions are "the right" conclusions or that he/she has discovered all the potential issues. But when we discuss these topics, we need to have a (shared) starting point, where everyone understands what particular terms mean.

# networks versus # (Global) networks