Generally I select material to sing that is from a traditional base, and if there is some connection with me on a personal level, be it where I come from, or who I have known, all the better.
However, what really motivates me to learn a song is the song itself. This could be the tune or the story or who the song came from - and really it matters not what the origin is.
I sing some songs that were collected hundreds of years ago, and some songs only written recently - but I approach their performance the same way. Yes I am an unaccompanied singer 99.9% of the time, so I would approach it from that angle, but I try and stay as true to the original as possible.
This of course is not to say I don't change words, or tunes to make it my own - and I do meld together different versions of the same song to achieve something that best represents the song for me and my needs. I believe that is what many old singers did, so I respect that aspect of traditional folk music.
Tim Radford (www.timradford.com)