Agreed and disagreed at the same time.
Regarding black box. There are a few methods I use which I do not go into detail with - not my clients, not my friends. It's not a magic sauce as much as it is protecting myself from competition stealing or copying discovered methods.
To the latter comment about hiring and firing them. Been there many times. It's suicide. A client is unhappy with results after a month, walks away, does his own SEO - see's a boost from the 1 month SEO, thinks they know SEO and then comes back crying 3 months later.