I think this post is proof that some people don't have enough activities in their life.
1. If a used sway bar had a problem, it would already be broken.
2. Even if it failed in use, the failure would not be life-threatening. A serious failure would be a ball joint or a lower control arm or a steering tie rod.
I've owned about a hundred cars, modified and hot-rodded many of them, and the only sway bar failure I ever had was the rear sway bar on a Lincoln Mark VIII. And, it failed because of internal corrosion. It is a hollow bar, and Ford failed to paint the inside, and failed to properly seal the ends.Water was trapped inside, and the bar eventually broke.