Just to be clear. There is no reason why a session factory HAS to be a singleton. The only reason is to save on the resources needed to create and destroy one.
Am I correct in assuming that a Hibernate program would work just as correctly using a non-singleton session factory, just less efficiently?

Is this really that difficult a question to answer?

I'm a newb, so i don't know, but I think there may be an issue with concurrent transactions and atomicity and such if you have multiple sessions, unless you do something special to avoid it. However, I'm just using a Spring sessionfactory bean and passing it into everything that needs it.

Actually, I think I'm incorrect. The sessions created by the factory are the ones that aren't threadsafe.

http://63-246-22-42.contegix.com/hibern ... tions.html

But i'd say it's pointless to have more than one sessionFactory. Please let me know if I'm wrong :-). But I wouldn't bother explicitly making it a singleton either. Singletons are bad, equivalent to globals. Dependency Injection is a better alternative.