Bolts work well enough in holding things together when the load is shear: so long as the two pieces are thick enough to distribute the forces properly, and the compression of the two faces is sufficient to keep them from sliding, you're golden. The load on a guitar bridge is _mostly_ shear, but it's that pesky torque lifting up the rear edge that causes most of the problems. In that case, once the glue (if any) lets go, the rear edge of the bridge curls up, and the top, in effect, curls down, so it just keeps peeling along. When the break reaches the bolts they are huge stress risers; much more rigid than the wood of the top or the bridge, so the load gets concentrated there. The amount of distortion you can see on a bolt-on bridge that has started to lift and not been properly cared for is really astonishing. Ultimately, if not repaired in time, the bolts simply rip through the top. Yes I've seen that.
The EKO 12 I got in Naples in, iirc, '69, had the solution for that: the bridge bolted through to a thick aluminum plate that spread the load. Oh; you want tone?
