15. The method of claim 14 further comprising: for a first user, allowing the first user to access the ontology data structures; and for the first user, disallowing the first user to access information stored as ghost edges or ghost nodes other than a first ghost node and ghost edges directly coupled to the first ghost node.
15. The method of claim 14 further comprising: for a first user, allowing the first user to access the ontology data structures; and for the first user, disallowing the first user to access information stored as ghost edges or ghost nodes other than a first ghost node and ghost edges directly coupled to the first ghost node. 16. The method of claim 15 wherein the first ghost node represents the first user in the social graph.