I've been reading about some peaceful protests (entirely unrelated to this one) and it is important to be aware that is possible that if "unsympathetic" parties want to shift the way the event might be reported, one way is to have people infiltrate the peaceful protest and provoke in underhand ways. This can manifest itself in any number of ways - someone continually catching the back of your heal, even a sudden outcry from someone - anything from claiming they have just been punched by [the nearest peaceful protester] or claiming their wallet has been taken and they know who did it [erm, the nearest peaceful protester]. Cue huge row.
Just be aware guys, I'm pretty sure none of these dirty tricks will be employed but don't be taken in. My advice still is that peaceful video cameras are taken to film the peaceful protest and to possibly catch any incidents like those mentioned.