I'm with Steve and PFR here. After all, if you look up 'Ballad' you get definitions as varied as:

1. Any light, simple song, especially one of sentimental or romantic character, having two or more stanzas all sung to the same melody.
2. A simple narrative poem of folk origin, composed in short stanzas and adapted for singing.
3. Any poem written in similar style.
4. The music for a ballad.
5. A sentimental or romantic popular song.

(Pasted from an online site, but my fat old OED lists a similar range of meanings)

If Jim, Steve and I are capable of sifting those and realising that the kind of ballad we're interested in is #2, I really don't see why we can't do the same with 'Folk Song'. Personally I think the old (1954 if you insist, yawn) definition is more coherent than "something sounding vaguely like a traditional song", "something sung to an acoustic guitar" or "something performed in a folk club", but dictionaries define words according to contemporary usage.