An article byabout the hidden dangers of climbing bolts:
Two climbers headed up a two-pitch sport route on the Fire Wall, above Tonsai Beach on the Phra Nang Peninsula of Thailand. At the two-bolt anchor, the leader pulled up slack to belay his partner, and as an afterthought, he reached up to clip the first bolt of the next pitch as a redirect to belay his partner.
When the second reached the belay, both climbers leaned out on the anchor to inspect the next pitch. Immediately both anchor bolts broke. The pair swung off their stance and hung suspended, 90 feet off the ground, by the single second-pitch bolt the leader had clipped as a redirect. That bolt didn’t break…
Read the whole article here: http://www.climbing.com/climber/built-to-last/