I scoured the forums and the docs - there's a lot of assertions that "it just works!" but few examples. For example, this quote seems to be out of date:
All seam example apps should run on a JBoss AS cluster.
I installed the seamdiscs example from 2.0.0GA under my JBoss 4.2.1AS configured for clustering, flipped on dsitributable and got a mess of NotSerializableExceptions when I tried to save anything. Of course, that could be a bug, but it's hard to tell sometimes:
Ah! I did find this gem which seems to be the most concrete bit of advice:
If you need to be cluster safe, hold the reference to the entity bean inside a stateful session bean (in any version of Seam) or inside a JavaBean Seam component that implements Mutable (in Seam 1.1).
But checking the hierarchy for EntityHome, I see MutableController implements Mutable. Clearly something's missing, but what? I'd be fine switching to stateful session beans if the ultimate answer is "EntityHomes don't work."