Thanks for posting this, Otto.
Actually it is much more of a problem than not at times.
Over time _as the floor gets its share of use and pounding, there is a tendency for nails to come through the wood, splinters to materialize and even glass fragments to appear out of nowhere...sharp objects have a way of finding a home on the dojo floor along with sweat and blood.
It is always a good idea to check the floor before a workout.
The dojo should be swept and mopped, sharp foreign objects removed, and any slippery areas on the floor wiped dry.