I have to admit, when Jim Titus suggested in the comments that we could provide helmets from vending machines near CaBi stations, I thought he was totally spitballing ideas. Turns out, Melbourne is doing it.
Melbourne Bike Share patrons would now have the option to buy $5 helmets from two CBD locations as part of a vending machine trial, or at 7-Eleven stores across the city.
Now, I'm not sure what a $5 helmet looks like or how well it works, but this does seem to be happening. I believe Australia still has a mandatory adult helmet law (as does Sykeville, MD apparantly), so there is more incentive to put on a helmet. But it may mean cyclists put the minimum helmet on to meet the standard (and hence the $5 price tag). They're also recycling them.
People can buy helmets for $5 and keep them, or return them to a 7-Eleven store for recycling and receive $3 cash back.