Helmet Laws For Motocyclists and Bicyclists?

If we want to get serious about decreasing the rate of head injury from traffic accidents, one way is to review the laws that could prevent many of them.  Although the National Transportation Safety Board strongly recommends the use of helmets and  "The National Highway Traffic Safety Administration estimates that helmets are 37 percent effective in preventing fatal injuries to riders and 41 percent effective for motorcycle passengers" there still are many places where helmets are not required by law.  

According to the Governors Highway Safety Association, three states (Illinois, Iowa and New Hampshire) do not have a motorcycle helmet law at all and 28 states require helmets only for some motorcycle riders. Further 21 States have a helmet law for bicyclists below a certain age, generally about 16.  An incredible 29 states have no bicycle helmet law at all.

What are your thoughts? Should helmets be required by law?