I see drawbacks to either approach. If the services can be shared across multiple SessionFactory instance then they *must* be stateless (or the state must be designed to be shared) which brings about portability/migration concerns. Additionally consider the case of "configuring" services shared across multiple SessionFactory instances; for example imagine changing the option to enable sql logging on the JDBC Service. Of course maybe that is what the user wants/intends so its nice from that perspective.

Really its a matter of the API for creating a SessionFactory. This came up in the IRC meeting. Its actually difficult to enforce that a ServiceRegistry only get used in a single SessionFactory.