I'm going to put my head above the parapet here, and say that in our family no-one wears cycle helmets.
We all cycle every day. DH does an 18 mile round trip to work, and the DCs do a five mile round trip to school, and I do a combination of school runs, and cycling around the city. We don't have a car so cycling is our main mode of transport.
DH and I have discussed it at length, and we've looked at a lot of research, and we're not convinced by the arguments. Since reading the thread again I looked again at a review of the research commissioned by the Dept for Transport in 2008 which recommended the wearing of cycle helmets. But the case is really not clear cut. For example, in hospital studies, which tend to show a stronger predictive protective effect of wearing a helmet (so they look at cyclists admitted with head injuries and say, this one may have been prevented by wearing a cycle helmet), there is no data on whether the cyclists were actually wearing a helmet anyway. So it is a prediction of what may have happened based on incomplete information. In hospital studies, around 10% of cyclist fatalities had head injuries which may have been prevented by wearing cycle helmets. When you extrapolate those figures to the general population of cyclists (ie how many fatalities there are per population of cyclists, or per miles cycled), you are looking at a fairly small predictive effect.
FWIW both DH and I have had accidents of the kind where a helmet might have a protective effect (I was knocked off my bike by another cyclist, toppled sideways and hit my head on the kerb, DH went over the handlebars) and both of us were fine. Our perception of risk is obviously influenced by our own experiences. In general we want to teach our children that cycling is a safe activity, but that roads are dangerous, and we are very keen to teach them good road skills. Wearing a cycle helmet, we feel, gives them the message that cycling is dangerous but that a helmet will protect them, which, in a road situation, is simply not the case.