As Pat mentioned, besides the issue of degredation depending on how long they were down(less of a problem with cedar), there is the issue of cracks, wind shear, ring delamination, etc. I don't like those kind of surprises. Bowmaking is a lot of work. I want to increase my odds of success when possible. I much prefer standing, living trees for all my bow wood just to be on the safe side. But if I was hurtin' for bow wood, it blew over recently at the roots, and that's what I had available, I'd go for it.