How Many Authors Does It Take To Promote A Book?

If it takes one author to write a book, how many does it take to promote it? The answer in this case is eleven.

There's a trend in indie publishing toward authors banding together to form a promotional co-op of sorts. The purpose of these cooperative efforts, or "lifeboats" as they are sometimes known, is to extend the authors reach and aid in "discoverability."
"Discoverability" being the new buzz word in publishing.  According to goodreads less than 10% of books are discovered by on...