I'm with Steve on the issue of overdecorated singing - I find it confuses my reaction to a song which 'should' contain some message or communication.

My earliest models (in Scotland) in the early '60s were singers such as Jeannie Robertson, Davie Stewart, Jimmie MacBeath and Willie Scott, and I was easily persuaded of the power of unaccompanied singing, particularly of the great narrative ballads.
And in the ensuing time I have had found no reason to change my mind! Now my main repertoire (covering ballads, lyrical songs, music hall, contemporary) is often unaccompanied.

Many previous posters have mentioned the difficulty of working with an accompanist -- or, at least, one who was less attuned than many. I have been lucky enough to work over the previous decades with a lovely guitar accompanist who actually LISTENS -- he totally pays attention to me (aurally and visually) and is always 'subservient', which is the best word I can think of in the circumstances!

But I would never imagine him accompanying me on a ballad...