Thirty year ago you'd never see a 'white bike' or similar memorial at a spot where someone died in an accident of any type. If the white bike is causing a danger to others (pedestrians, other bicycle riders, vehicles), then it should be removed as it could cause problems itself. If its on private property, then the property owner should have given his/her blessing before it was installed. A lot I've seen in Southern California just turn into eyesores as the bicycle deteriorates and becomes a rusty hunk after 6 months.
FWIW: Not sure of this, but it appears whenever someone gets killed in a bicycle accident around my area, and a white bike memorial is set up that doesn't interfere with anything, the City will leave it up for a few months before removing it. There are plenty of flower memorials around town (vehicle accidents), some I know have been in place for over a decade; one on my way to work has been in place over 15 years and, although it has shrunk in size, its being well-maintained.