This topic has popped up a bit a few times recently. It's something I feel strongly about and I mentioned it in my post on Books on Preaching a few days ago. Jollyblogger has been reading old Journals of Biblical Counselling and has found David Powlison writing on the same subject. And Sinclair Ferguson ranks it at No. 5 on his Ten Commandments for preachers.
The more the merrier! All for the sake of better preaching.