This isn't really different from a "Bed of nails" when you get down to it - one nail will go through a person if you put all your weight on it, but if you divide your weight over 400 nails, then each nail is only applying 1/400th of the pressure on its point. It will be slightly uncomfortable, but it won't actually hurt you.
The real torture devices are designed to gradually force the person into the spikes as the pressure is cranked up. If you look at those are braces, they are loose, but have spikes on them as well. If you keep tightening them, it will force the victim into the spikes from both sides, but as it sits, those straps are too loose to do damage.
