[Ray H]

If you are doing a straight pull, It wont be the frame thats the limit, it'll be the pull points (ie, hitch, winch mount, towhooks, etc) that will give way. Thats assuming your winch cable doesnt break or your winch doesnt simply stall first.
This is where your accessories come into play. By using snatchblocks to double or triple the winch cable you reduce the load on the cable and on the pull points and increase the power of the winch (a pulley system). This is a much safer way to perform hard pulls than just simply running the winch cable out and hoping for the best.
I think a winch in the 9000lbs range is a good match for a Jeep. If you need more winch than that, you should be using a snatchblock to reduce the stress on your pull points and cable anyway. If you want a 10000 or 12000lbs winch, more power to you but you should still be using a snatchblock.
If you really want a winch to help your friends, not so much for self recovery, look at the Milemarker Hydraulic winches. They pull strong, they dont overheat and they are just plain cool. Their big drawback is that your engine has to be running for them to work. That can be a problem for self recovery. Thats the only reason I chose electric over hydaulic when I got mine.