Your examples are right on… I would further refine affinity groups to include real-world associations and groups such as the American Heart Association or IEEE that have a much better defined purpose, than say Orkut, and a real-world social network already in place. I would also add Groove Networks as an example of Shared Spaces.

The key, as you describe it, is really being able to segment content into many different “spaces” - designated by the content owner and ranging from the public Internet to varying degrees of privacy/visibility.