Good points, Howard, even though I disagree on some. But that is what healthy discussion is all about :-) I would define Folk Rock as a genre that uses elements of both folk and rock music as its structure. As such it is independent of types of instrument although a driving rhythm is required to fulfill the rock element. There are Steeleye Span songs that do not have any rock element and I would not place in that category but, in the main, they are the archetypal folk rock band. Blackbeards Tea Party make good use of percussion and bass to provide that rock element and, again, in the main, they are good examples of Folk Rock.

Following that through, if we look at the development of rock it came from rock and roll which in turn came from blues which came from gospel, jazz and country amongst many others. I think it fair to say that, although the term was not coined until the 1950s, rock has always existed and in folk music, particularly dance. Those driving rhythms that we now term Folk Rock have been around forever!