Just to add some fuel (not that its needed) to the ever-raging helmet debate. I got knocked off my bike last Sunday. Oncoming driver "didn't see me" (I know I've lost a few kilo's on iDave but I'm not THAT tiny) and turned right across my path taking my front wheel with him. Wheel: pringled, carbon road bike: smashed, me: supermanned across junction with direct blow to the top of my head from his car/road (I'm not sure). Picked myself up and walked away from accident. Witness called ambulance and police. Paramedics took one look at the helmet and stuck me on rigid board with collar. I had a few abrasions on limbs and additional bald spots from where I got "scalped" as I blew through the helmet, broken L ring finger and spent hours in A&E getting my c-spine (thankfully) cleared, then spent a few more hours on an observation ward after the consultant saw the helmet and thought I might need a CT (I didn't).
Driver got done for driving without due care and attention (to give him his due he was very shaken up, but admitted full liability to me, witnesses, paramedics, police and his own insurance co). I missed 1 day of work because I was achey and had to go to fracture clinic about the broken finger.
Do you really think I would have got off so lightly without the helmet?