You've probably seen a few videos like this on YouTube:
The frightening reality is rack collisions happen often. Some result in dings and bangs to equipment and rack. But, some like this one above results in massive losses in equipment, inventory. (Some accidents also have tragic results.)
Pallet rack is the most common storage product in the industry. And it is better engineered than ever. But even with better technology, like energy-absorbing materials, collisions are inevitable.
These kinds of incidents can be easily mitigated however.