I try not to jump off cliffs and stuff like that..
Well, there is risk in everything, most of it is not in the actual activity. For example, sky diving is pretty safe, statistically and everybody mentions flying is safer than driving. However, like mountain climbing, most mountaineers list subjective dangers verses objective dangers. These dangers or risks are not just for mountain climbing and can be applied to every day life. Like me, biking to work, I have to face subjective dangers all the time.. i.e. say passing another slower cyclist or perhaps biking to work in a snowstorm. These are dangers I have some amount of control over. Compare this to objective dangers like a tree falling on my head or a drunk driver taking me out from behind. To a point, one can't control them.
So, as a person who doesn't want to get injured, there are subjective hazards you can avoid by perhaps not jumping off cliffs and things you can't. I try to avoid subjective dangers and so far, haven't had a problem in 5 years of bike commuting.
I still don't jump off cliffs though.
I realized I didn't really answer your question about motorcyles... Did you hear about Ben Rothlessburger (sp?)? Strange enough, I read about him on a cycling forum (other than the news), he was riding a Hayabusa in urban pittsburgh, without a helmet, without a motorcycle license and probably without any formal motorcycle training.
As I see it, that is a huge amt of subjective risks he was taking:
1)Urban riding
2)very very powerful bike, probably way too much for his experience
3)no license and probably no training
Having said that, I believe reading that the lady who hit him ran a light that was out (not working) so the accident itself was perhaps out of his control. Ultimately though, he should of been wearing a helmet, helmet law or no helmet law, his skill level and the dangers of urban riding, I'd wear one and that is under his control.
About you, how do you consider your friend as a motorcyclist, is he/she a risk taker, known to push the limit, or is he/she somewhat conservative. What kind of ride is it, open highway, a parade through Lincoln, NH? or something similar. You have to decide on the skills of your friend as you have no control being a passenger, the situation (include the weather for this.. rain, etc..) and then make the decision yourself..
Jay