»In which have a moment of silence

Reading an article about another hit-and-run in which a motorist kills a cyclist and then drives away makes me all the sadder for Sarah Tucker, who was killed in San Francisco nine months ago, and whose murderer has not been caught. Oddly, the San Francisco Bicycle Coalition has taken its memorial for Sarah Tucker off-line.
I read about cyclists killed in the middle of the day, in the middle of busy areas, and wonder: how do people escape, or think they can escape, the responsibility for these incidents? Do they think that cyclists wearing helmets make better targets?