Where has the owner field of struct proc_dir_entry gone? [ Linux Kernel ]

According to the list of API changes in the 2.6 kernel series on LWN the .owner field of struct proc_dir_entry was removed in the 2.6.30 Kernel.

So here's a couple of questions:

1. Was it really ever necessary or useful to set this field?
2. Has the field just been moved somewhere else, or permanently deleted?

I ask the first question because while the LKMPG set's this field in many of it's examples, procfs_example.c from the Kernel Documentation never does.