Steven,
Look at this beautiful exercise sheet from Oreilly -
http://examples.oreilly.com/hfjejb/EJBSharpenA.pdf Page five has a nice matrix of different characteristics of the four different bean types.
It says about the pool:
Stateless Session Beans: Yes. Since they don't keep and client-specific data, you don't need one per each client.
Stateful Session Beans: Nope. Stateful beans never have a pool.
Entity Beans: Yes. When an entity bean is not *being* a specific entity (row from DB), it stays in the pool.
Message-driven Beans: Yes. They're a lot like statelss session beans. Any bean of a particular type is the same as any other.
Regards,
Dan
[ January 11, 2005: Message edited by: Dan Drillich ]