One of the things often practiced by Search Engine Optimization companies is that they don’t disclose the SEO process they do. Sometimes they don’t even disclose the names of their clients. If they reveal who their clients are, it becomes easier for others to examine them (page title patterns, keyword density, inbound links) and possibly find out what the SEO processes are.
It’s understandable that companies commonly hide their SEO processes. While it cannot be called patented work, the process and methodologies developed were product of acquired knowledge and years of trial and error and findings of SEO experiments. It would be unfair for someone to get hold of these information overnight while it took years of sleepless nights for someone else to do the legwork.
Some people call certain optimization methods as secret while others see them as common sense. I think if there is a secret with SEO, that is how search engines develop algorithms but even that can be tested. Otherwise, in the field of search engine marketing, nothing seems secret; revealing this search marketing secret is an escape from ignorance.