When should EJB3 entities implement Serializable?

[vk101]

I seem never to need to use Serializable, whether or not I'm using Remote or Local interfaces. I thought if you use a Remote interface, then you must...or not? When is it required that you use them?

Are EJB3 entities the only thing that would need to be Serializable, or is there anything else as well (e.g. session beans, utility classes, etc)?

[varunnarang]

The only reason, I can think of, for entity implementing the Serializable interface is so that it could be sent as an argument during remote invocations.
Otherwise an Entity in EJB 3.0 need not implement it.