i can think of few use cases where i would use named graphs, possibly it could work similar to level-sublevel ?

i would like it mostly for provenance, so when i aggregate data from various sources i can keep it in named graphs!

for example if one publishes list of one's friends using foaf:knows predicate, one could also add triple stating that https://twitter.com/pontifex knows her/him. I might like to check such claims for example against http://vatican.va and would prefer not to put everything into the same graph...