One thing the Occupy protests have brought back into the public eye - if you haven't done a lot of reading about the anti-globalization movement, anyway, which is where a lot of these tactics got pioneered - is the mass arrests that happen whenever there's a large, confrontational rally.
Example: The recent arrest of 409 Occupy Oakland protesters.
At first glance, this raises the (terrifying?) specter of hundreds of angry protesters committing crimes - and then being caught by police officers, charged, prosecuted, and convicted.
Looking at the actual numbers, though, turns up something that might seem puzzling. Of 409 arrestees, 12 were charged with crimes - that's just over 3%.
12 of 409. That's not very many at all. So why arrest 409 people?
Well... for one, it's a quick way to break up a protest. If you've got a bunch of people that you don't want protesting, there's a simple way to get rid of them: Pen them in so that they can't go anywhere, and then arrest them all for failing to disperse or some similar charge.
This is what the cops did on the Brooklyn Bridge, where 900 New York protesters were arrested: they let the protesters onto the bridge, then closed off both ends and arrested them for disorderly conduct.
In that case, we saw another tactic, and one that reveals the directly political nature of the arrests: the protesters were released with the understanding that if they were arrested again within six months, they would be charged. The National Lawyers' Guild, which represented the protesters pro bono, spoke of a "chilling effect" that such a tactic has, and rightly so.
The police say that there's no political side to this:
The district attorney’s office does not agree that ACDs have a chilling effect on protesters. The source said that if protests are peaceful and “if you are not breaking the law, you are not going to get arrested.” But if people are doing “everything lawfully and they still get arrested,” a source in that office conceded, then the decision about whether to prosecute is “at the discretion” of the district attorney.
So. Mass arrests to end protests (though whether those arrests actually serve that purpose or not is up for debate; it didn't work in Oakland), followed either by no charges or by charges designed expressly to keep people from protesting further.
Does that sound like what the cops are supposed to be doing to you?