What is a “staff scientist” and is this an attractive career option?

Our good blog friend, occasional commenter and behind the scenes provoker of YHN’s blogging nearly on par with CPP, @superkash put up a twitt poll:

how many postdocs would be interested in a staff scientist position, if only for 5 years.

— Tom Kash (@superkash) January 16, 2017

An extended discussion is going on and there are a few things of interest to me that are emerging.

What IS a “staff scientist”? Does it have a defined role? How is it used both formally by institutions and in less formal career-expectation space? How is it viewed by the hiring PI? How is it viewed by postdocs?

Is it, or should it be, a mere evolution of a postdoc after a certain interval of time (e.g., 5 years)?

Is it, or should it be, in part a job-job where a person is hired to do one sciencey thing (generate data from this assay)?

Is it, or should it be, a job where the person “merely” does as the PI instructs at all times?

Does it come with supervisory responsibilities? Is part of the deal to remove this person from ever having to consider grant-getting?

Is permanence of the job in a way that is not the case with postdocs an implied or explicit condition of the job title?