While the fundamental purpose of the Occupy Wall Street protest was to draw attention, the problem with an "Occupation" as opposed to a kind of rally type protest, even a rally that occurs on a daily basis, is that an occupation carries the risk of wearing out your welcome and then instead of building support, the protest tends to lose support at best and generate outright opposition at worse.
I will be the first to defend the rights of the occupiers to make their protest even if I think much of their message is silly. But like with all long term protests, there takes a bit forethought and cooperation with the locals to makes sure basic things, like hygiene are considered. As one story I have seen discusses, protesters are defecating on private property. Furthermore, locals are being harassed while going about their daily business and the protesters are apparently making noise at all hours of the night.
Manhattan is a particularly difficult area to protests. Unlike a lot of "business centers" in major cities, Manhattan is also a very residential place, making clashes with local residents much more likely.
Protest all you want, but when you start disturbing the rights of others, there has to be some limits, even if it means disbursing every day.