Emmanuel says in http://forum.hibernate.org/viewtopic.php?t=961140,

 [quote]I also know we need to fix some limitations regarding associations table updates / delete and bulk operations[/quote]

This issue provides a reminder that this task is pending.

For bulk deletes, consider this scenario: Assume Person and Group entities in a bidirectional ManyToMany relationship with Group as the owning side. This implies a Join table, with the default name of Group_Person. Currently issuing

em.createQuery("delete from Group").executeUpdate();

makes no attempt to delete the corresponding rows from Group_Person, even though Group is the owning side, giving constraint errors. Since Group_Person has no corresponding entity, I don't think the spec's prohibition on lifecycle operations or cascading applies here. The only workarround is to individually delete the Groups.
--keenan