Running around Town

Just to clarify: I wasn't the one doing the running. Tomorrow is the Chicago Marathon, so the streets have been filled with skinny people, running. I passed quite a number of them as I made my way (walking) to the Cathedral for Mass this morning. And this afternoon, when I went up Michigan Avenue on an errand (driving), the sidewalks were packed with shoppers. Presumably the 20,000 marathoners and their cheering squads.
Adding to the general throng was (and is) a voluble group of protesters, presumably "Occupy Wall Street." I say "presumably" because a few minutes ago they passed across the street chanting about corporate greed, but yesterday (which seemed to be their organizational day), the Randolph Street staging area was arranged with signs and flyers demanding jobs and protesting NATO involvement in Afghanistan. I don't know if that was only for yesterday, or if today's march (in the early afternoon) was a catch-all protest, and only a hundred or so die-hards remained 'til the late afternoon to make their point about corporate greed which is, yes indeed, a very bad and damaging thing. Their chants are still echoing in such a way that the sound penetrates our house (what a distraction in chapel!), but you can't tell from which direction. Just a vague noise, punctuated by occasional cheers and whistles. A bit unsettling after a full day of it.
Here in Chicago there is also a regularly scheduled "protest" involving hundreds of bicycles on the major roads on particular Friday afternoons. Something about taking "back" the streets. It ties up significant resources from the police department, since there is such risk of injury to the cyclists.
I like bikes. I agree that war and greed and unemployment are all evils that should be eliminated to the extent possible. I pray for that!  But what good do parades do?
Do such demonstrations contribute something positive to public discourse, or are they just a form of entertainment? I'm beginning to think the latter.