The benefit here, I guess, that you get the advantages of sequential IDs internally? I can't see how this could possibly outweigh the costs of user-visible IDs

The benefit here, I guess, that you get the advantages of sequential IDs internally? I can't see how this could possibly outweigh the costs of user-visible IDs being different than internal IDs, and transformable only thru a {de,en}cryption process -- requiring all the standard maintenance, key rotation, etc.