China's Pedestrian Glass Bridge has cracks.

[bing101]

http://www.washingtonpost.com/news/morning-mix/wp/2015/10/07/chinas-new-glass-bottom-bridge-cracks-3500-feet-above-earth/

And this bridge is fairly new. It's supposed attract tourists to the Chinese version of Grand Canyon

[Duke87]

Anything made of glass can and will shatter given the appropriate impact. That's why there are three layers of glass. Only the top one broke. If the owners of the bridge are maintaining it right, they will replace it right away with a new one and that will be that until the next time someone drops something heavy on the bridge.

All glass-bottomed structures are susceptible to such things and must be multi-layered for redundancy. The overlook boxes on the Sears Tower observation deck have had floor panes crack. No one has been hurt and they simply replace them.

This is only freaky because:
1) This bridge takes the glass-bottomed thrill to a level considerably above what is typical
2) It's China and they have a reputation for poorly constructing things

Realistically the biggest risk with this is someone slipping and falling on the bridge. Glass isn't known for having lots of traction.