While I understand the safety arguments for encouraging people to ride on separate bike infrastructure, I generally think this is a pretty short-sighted attitude; cycling will never achieve the level of convenience necessary for it to attain a reasonably high transportation modal share if the recommended practice for cyclists is to take circuitous recreational paths through parks instead of the much-more-direct routes available to motorists. Look at any cities in Europe that have reached moderate cycling modal share (Amsterdam, Copenhagen, etc.), and you'll see that while grade-separated cycling infrastructure is common in high-traffic areas, it follows the same routes as cars (complete with traffic lights), and that cycling on same-grade painted lanes is common in lower-traffic areas. Nobody is pushing cyclists in these cities onto inefficient completely-separate bike infrastructure.

Thanks for the link. I was dimly aware of some arguments against wearing helmets but haven't examined the issue in depth.