Answer:
I have a name that's not mine and no one cares about me in their prime. People cry at my sight and lie by me all day and night.
The more you have me the less you see. Shine a light on me and I shall flee.
Though desert men once called me God today men call me mad. For I wag my tail when I am angry. And growl when I am glad.
Though it be cold, I wear no clothes. The frost and snow I never fear. I value neither shoes nor hose and yet I wander far and near. What am I?
You use a knife to slice my head and weep beside me when I am dead.
The answer I give is yes, but what I mean is no. What was the question?