The Tea Party formed pretty spontaneously. It got its start when a commentator on CNBC suggested that people throw a new tea party in response to the government's most recent bail-outs. In retrospect, the spark that started the Tea Party didn't amount to anything. President Obama had announced a new program to help mortgage-holders who were having trouble making their payments. The outrage came from people who resisted getting so deeply into debt and felt that their tax money (plus debt accumulated) was going to subsidize bad judgement. The irony is that the mortgage-bailout program was a total flop.
The left assumed that the Tea Party was somehow an example of AstroTurfing (creating a centrally-managed campaign disguised as a grass-roots movement). They were wrong. The Tea Party was a real, wide-spread movement as shown by its success in the 2008 elections.
One of the hallmarks of the Tea Party is how orderly it has been. It has been a matter of pride for organizers that protests do not break any laws and that the protestors pick up after themselves. Politically it is a form of populist libertarianism, strongly influenced by the writings of Ayn Rand.
OWS has very different roots. It was planned weeks in advance by a group created for this purpose - October 2011 (O-2011 for short). O-2011 is affiliated with numerous other groups including Intentional ANSWER and Code Pink. Politically it represents the hard left and many of its affiliates are outright socialists. During the first couple of weeks of the protest signs saying "socialism now" or similar were common.
Where the Tea Party prides itself on following the law, the OWS had 700 arrests over the weekend. Police have been forced to use pepper spray (with video showing that they were provoked).
The OWS movement is part of a series of long-term protests set up by activists who have rejected democracy. It started in Wisconsin and Ohio in protest of union-busting legislation. Not surprisingly, several labor unions have expressed support for the OWS. All of this is influenced by the Arab Spring protests.
O-2011 is trying to be a throwback to the glory days of the 1960s and early 1970s when mass protests were common. Of course, those were mainly for racial equality or against the Viet Nam war (or both). One giveaway is the symbol used by O-2011 - a black fist with the Earth superimposed on it. This fist was a frequent symbol of resistance during 1960s protests and continues to be used by socialists. In fact, the black fist has its own Wikipedia entry.
Democracy is a simple idea. It means "the people rule." The promise of the United States is democracy. The reality is that corporate elites rule. The contradiction between the promise and reality of America has produced a movement to make the promise the new reality.
So, to this movement, elections and elected representatives no longer matter. All that matters is who can put people in the street.
The OWS protestors have pledged to remain as long as it takes. This looks like it will be a long wait since the movement purposely kept its goals vague.