For all the hundreds of people who talk about wear from the inside out of the tire from beads I have yet to see a single picture of any tire being worn out. When you consider the weight, size and the beads being spherical I just cant see how they could possibly wear a tire out. Also many manufactures recommend them for the use INSIDE of motorcycle tubes.
I don't think lead would be such a good idea its already banned in some states for the use of wheel weights. I also wouldn't want to be around when the tire was dismounted or aired down. I would think there would be a considerable amount of lead in the air.