During the Bush years, one influential person made a common appearance on the political stage -- Some Guy With a Sign. No matter what you needed to have your opponents say to discredit them, Some Guy With a Sign could be found, somewhere, to obligingly have his sign say it. The right-wing media were champions of this technique, only occasionally overreaching, as with amateurs like Donald Douglas and "Sasquatch Israel". The left, of course, had the Morans! guy, but didn't have Fox to catapult the propaganda. The electronic version of Some Guy With a Sign is Some Guy With a Blog Comment, commonly held to discredit everything written on that blog, or indeed everyone on the same side of the political spectrum.
This is a bit different from the right wing's use of agent provocateurs, such as Patrick Howley, the editor of the American Spectator who openly boasted about trying to get Occupy protestors to turn to violence. Any really good Guy With A Sign could be an agent provocateur, of course. But it's not required. It's impossible to police and discipline every sign brought to this kind of demonstration, or to anything that has a contemporary style of mass involvement without a leadership cadre. And some of those signs are going to be brought by crazy or ignorant or bigoted or self-promoting people.
The Occupy version seems to be Some Guy at a General Assembly, as seen in this iconic picture (they are always iconic pictures, if they catch on) of Some Guy Marginalizing John Lewis. Some people gamely try to make the argument, in comments, that John Lewis is a politician and the movement can't let itself be taken over by politicians etc etc. Which just doesn't work. Any press flack, if Occupy had such things, would have said something like "Geez just let John Lewis talk for a while, then we'll go back to whatever we were doing." But Occupy doesn't have press flacks, leadership cadres, or any of the other things beloved by our mass media, so these scenes are inevitable.
I wish that people could move to a style of defense that doesn't involve denouncing Some Guy With a Sign, and that doesn't involve saying oops we are so sorry and blaming it on the "process". It's an unguided popular movement. Things are going to happen. We have a media addicted to sanitary photo ops, which loves to treat pictures like this as if they mean something symbolic, but really, what they mean is that in a consensus-driven general assembly, some guy named Joe can have a bad day. That's pretty much it.
If the general assembly was supposed to be a cadre making decisions, then sure, it's a very bad way to do that. But it's not. It's supposed to be a way for people to talk to each other, basically. People made fun of the grab bag of Occupy Wall Street demands, which I'd guess were indeed just a grab bag of things that someone got up and said and other people cheered to and that got written up. But the real point of Occupy is that the people are there, warts and all.
ETA: "Anarchists for good government", and the sign "Our economy could be more fair". (Via here) You can find vaguely British understated humor in these signs too. "Anarchists for good government" is worth coming back to, though.