Wanted to mention that there are back protectors available. They are a little uncomfortable at first, but when you get used to it you won't even notice that you have it on. Also protects the bottom of the neck a little.
I always wear some kind of back protection when riding. I'd agree that it really doesn't take much effort to add it, and you won't notice it beyond initially putting it on (though sometimes it will effect airflow on hot days - still, after time it is not noticed). There are also many jackets that have spine protectors integrated into them. Bohn Body Armor makes some good spine protection in various sizes, one of which integrates into the Aerostich jackets (rider wear of choice of the circles I ride in). In addition there have been many recent advances in developing more comprehensive protection for the spine and neck in the form of motorcycle airbags, and hard solutions like BMW has been looking at. I was recently in Hawaii where motorcycle wear seems to be limited to t-shirts and flip-flops, largely because of the heat and humidity. Regardless the sight makes me wince. I'm all for freedom of choice, and where the helmet laws are concerned I see it as a Darwinian way of thinning out the population of really stupid people. The only problem with that is ultimately it jacks up all our insurance rates and perpetuates biker stereotypes that other stupid people seem all too willing to embrace.
Just as the room is as critical a component as any other in our systems, just as important as the protective gear motorcyclists wear is the attitude which has been echoed here by many experienced riders: Ride as if you are invisible to others. I also do everything I can to make myself visible to others, such as high-beams and auxiliary lights on-always during daytime hours. Our brains perceive distance and speed via our two eyes (much like our two ears can perceive dimensional perceptual cues). An oncoming vehicle with a single light is far more difficult to gauge speed and distance. Two lights spread as far apart as practical on a bike will lend at least some band-aid to that. As a car approaches the two wide-spread lights appear to go from small and close-together to wider-and-wider spread apart. This is a vital cue to oncoming drivers to help gauge oncoming speed and distance, as well as being more noticeable simply by having multiple lights. A single light practically obliterates that cue and makes it more difficult to gauge oncoming speed. THE most frequent accident for motorcycles in a multi-vehicle accident is being cut off by a motorist turning left in front of an oncoming bike (this from the dated Hurt Report, seems to be confirmed over and over in more contemporary studies of accidents). The most frequent reason given was that the driver either did not see the biker or did not realize how quickly they were approaching.
Regardless of all you do to make yourself noticeable, I would still ride like you are invisible to others. The consequences of not doing so in this country are far too great. In many other countries there is a far greater respect and awareness of motorcycles and scooters and bicycles on the road. Perhaps as gas becomes far more expensive, and more people in this country turn to these alternative forms of transportation, there may be some small steps in that direction. Banning hand-held cell phone use while driving on public roadways would be a step in the right direction, IMO. But now I digress, as usual.
Marco