Can I just say...
"Would you prefer to be shot in the head whilst wearing a cycling helmet or whilst not wearing one?"
Please feel free to explain your answers using maths and physics, referencing the transfer of kinetic energy and the effect of rapid deceleration on the human brain rather than anecdata.
Bit of a silly post. If you come off a bike at 40mph and land on your head then it probably won't matter whether you are wearing a helmet or not, the outcome would still be the same.
It's at lower speeds where it becomes a grey area IMO, but at the very least a helmet protects you from cuts, grazes, the side of your head scraping along the road etc and that's good enough for me even if it doesn't make any difference in an impact situation.
However, I still stand by my post from earlier whereby if you hit a wall or fell at slow speed it would hurt a whole lot less with a helmet on. And a point impact would at least spread the force somewhat - imagine a flattened out helmet on a table, hit the table with a ball hammer and you'd damage the table at that point. Hit the helmet with the hammer and whilst the same overall impact may be applied to the table (if the helmet material didn't compress, if it did then the energy transfer would be reduced) the load would be spread instead of being concentrated at that point.
ps: Good post above bianchi. There is no right or wrong, just personal choice and nobody should be derided for making theirs.