The set of resources exposed by the API is not 100% self-contained, meaning that some resource hrefs need to be created ad-hoc without being able to list the corresponding resources using an index (GET) call, which includes accounts.
Some resources will only be exposing a basic subset of their existing attributes and/or relationships. (Note: There are plans for more attributes and relationships to be exposed as the API evolves.) For example, when API 1.5 was first released as beta, neither servers or deployments could be locked via the API. However, that functionality is planned.