We were walking along with our walking group one day and suddenly one of our walkers fell forward for no aparent reason and smashed her face into the ground. It turns out that it was caused by the killer boot hooks. Many manufacturers of boots have hooks for laces at the top part of the boot. It is very easy to catch the loop of one boot in the hook of the other boot. At this moment the walker will crash to the ground. Many serious injuries and maybe some deaths have been caused by this and we would like to draw attention to this problem.
The easiest way is to not buy boots which use open hooks. After that you can just remove the dangerous hook with a pair of pliers. If you are really gifted you can buy some eyelets and reinforce the holes with metal. If you don't want to damage your boots always remember to double tie your laces leaving small loops that can't catch on the other boot.
Here is a video which demonstrates the problem.