Bow saws have a real advantage for cutting pulp wood. This said, they are extremly dangerous because of the increased area for kickbaack to occur, and also when cutting through a log is not careful the blade hangs below the saw (loop) and can contact a leg if you get lazy with your cutting. Here in South Carolina small time pulpwooders still use the bow saw. One major advantage is that it is a lot harger to get the blade of a bow saw pinched. I have seen a man cut logs that were laying on the ground with tension on them, from the top side all the way through with out binding the bar. This cut would have never worked with a conventinal straight bar. Also the bar limits the diamer of trees that can be cut but can still cut around 22-24 dbh trees with them (i have seen it done).
Yes people still use these saws around here, i saw them in use this last summer by a logger that worked on the army base i worked at.