I remember quite a while ago seeing (on White Blaze, long before this forum existed) a math formula for the force exerted on the hammock suport line given the weight being supported and the angle of the lines from the trees. When I used the formula for myself (about 185 lbs at the time) I got about 600 pounds on each line at somewhere around 30 degrees? Given what I'm reading above, maybe my memory isn't too good. But if the rating is 200 pounds and the breaking strength is around 800 pounds, it's not supprising that people are bending them.
I'm using the ring buckle system now and I think I'll stick to them instead of these things. Hopefully, I can find the formula and post here later.