Originally Posted by Leo C. Driscoll

In Boston, bikers "share" sidewalks with sleep walkers. When looking at the backs of sleep walkers, I use the brass model of the Incredibel and reward their sideway move with a "Thanks!". When riding head-on and looking at sleepwalkers' heads down and their eyes riveted to the sidewalk or when their heads are attached to a cell phone, I use a horn (while playing a fugue on the brake levers). (I also use the horn when a Rattus Norvegicus is running across my path when I'm spinning down a Fenway street.) When commuting at night on sidewalks and narrow-bridge walks, I use a Cygolight 15-watt setting, pointed down so the sleepwalker doesn't act like a deer frozen in the headlight. On Fenway (mugger) trails, I use the 25-watt setting, not pointed down. When approaching a crowd of thugs or a drunken crowd of college kids, I brake, and let them pass me (with a cartridge of pepper spray strapped to my left glove). You probably don't need the pepper spray, but check out the following for bells and horns.
http://sportsbay.com/bellsandhorns.html
On a positive, note, pedestrians can be a blessing. I frequently run errands on my 1984 Raleigh Technium single-speed, negotiating my way through thousands of students on the BU campus. This is an incredible (but not Incredibel ;-) training experience. Bring on the single-track after weaving and broken-field running along Commonwealth Avenue at high noon!