NEW YORK (CNNMoney) -- Hundreds of demonstrators took to the streets of Manhattan's financial district on Saturday in a largely peaceful protest aimed at drawing attention to the role powerful financial interests played in wreaking havoc on America's economy.
Modeled on the "Arab Spring" uprisings that swept through Egypt, Tunisia, Syria and other countries this year, Occupy Wall Street is a "leaderless resistance movement" orchestrated through Twitter, Facebook and other social media tools. The Twitter hashtags #OccupyWallStreet and #TakeWallStreet lit up Saturday with coordination messages and solidarity tweets. (See CNNMoney's coverage in photos and tweets.)
Activist magazine Adbusters spearheaded the event, putting the call out two months ago for participants in a Sept. 17 demonstration in lower Manhattan. Protestors arranged to meet and discuss their goals at the iconic Wall Street Bull statue at noon, as well as at a "people's assembly" at One Chase Manhattan Plaza at 3 p.m.
"The NYPD is aware of various protests and we have planned accordingly," Deputy Commissioner Paul Browne told CNN late Friday.
Early Saturday morning, police barricaded off Wall Street, erecting barriers around the bull statue that protestors had planned to make their rallying point. Protestors instead took to the surrounding streets, blocking traffic. By 2 p.m., nearly two dozen uniformed police officers surrounded the bull, while others worked to disperse the crowd.
"None associated with the demonstrations sought permits," Browne said Saturday. "A group that formed at the bull at Bowling Green spilled into the streets on each side of the bull, posed safety issues and impeded vehicular traffic. The streets were re-opened to vehicular traffic and barriers were subsequently erected at the bull to prevent a re-occurrence.
A marching band played as participants held impromptu yoga and tai chi classes in Bowling Green Park. Demonstrators moved their protest to another nearby park as their numbers swelled to around 500.
"Something needs to change," said one protester, who declined to give his name and covered half his face with a bandanna. "We need an economy for the people and by the people, not for the rich and by the rich."
Another protester, Rheannone Ball, chimed in: "It's our duty as Americans to fight for our country and to keep it true to serving its people. When it doesn't do that, it's immoral not to stand up and say something."
A call for 'justice:' Kalle Lasn, the editor-in-chief of Adbusters -- an activist magazine with a worldwide circulation of 100,000 readers -- said the editors there are angry that leaders in the financial sector "had not been brought to justice." Their inspiration came when pro-democracy uprisings broke out in Egypt on January 25 and quickly spread to other countries.
"We thought, why isn't there a backlash here?" Lasn told CNNMoney in an interview before the event. "We need to shake up the corporate-driven capitalist system we're in. To do that, we needed something radical."
Last month, cyberactivism group Anonymous released a video in support of the protest.
"It gave us a nice bit of street cred, some mystique. We lefties need a lot of mystique," Lasn said with a laugh.
That mystique is what drew Josh Dworning, a 20-year-old college student, to shell out $300 for a 24-hour train ride from Florida to New York.
"I heard about the protest through StumbleUpon, and I just really agreed that there's widespread discontent with the banks and corporations," Dworning said. "I'm no crazy radical, just a student who believes in something."
Dworning, who brought a tent for camping near Wall Street on Saturday night, said he's "planning on staying as peaceful as possible" -- though he'll be on alert, because "there's always the chance that someone can get a little too angry and throw a brick or something."
That's what scares Dworning's mom, Jeanne Molle, who said she's "a nervous mother watching her son get involved in a large-scale event in [a huge] city."
Lasn is hoping safety won't be an issue. A "Gandhi-like peaceful protest" is the only way the event will work, he says, though he acknowledges that central control is impossible over a group that organizers hope will swell to 20,000. And "there is a question of legality" around setting up tents and barricades, he admitted.
In a September test run of the occupation, nine people were arrested for disorderly conduct, and later released without being charged.
"It takes a lot to rise up and reform the global economic system," Lasn says. "And maybe this time we fail. But if we do, we're just setting the tone for the next revolution." 
