PhD holders make contributions outside academia

I have not heard the term/occupation of "independent scholar" until I read an article from The Chronicle of Higher Education (dated Janaury 21, 2013). According to the author, scholars chose to be an "independent scholar" for many reasons such as unable to land a tenure position after applying for more than 30 positions, Finished a PhD at the age of 47, family resposibilities etc.

Being an independent scholar sounds very attractive  - compared to tenure positions at universities, it has less stress, working full-time on research projects and/or writing books.

The title of the article is, "Some Ph.D.'s choose to work off the grid":
http://chronicle.com/article/Some-PhDs-Choose-to-Work/136729/