More accurately what it requires is overwhelming opposition to existing security forces. That's really the difficulty here, in Seattle N30 the anti-globalization movement managed to pull it off - primarily by surprise. But as seen at the Miami FTAA protests, the government wised up and thanks to 'homeland security' initiatives has significantly beefed up its numbers.
The lacking ingredient here is not so much training or arms, its commitment. Mark Rudd put it best when he said that the state has claimed a monopoly on violence, and any violence NOT sanctioned by the state is considered criminal or insane. If you have that viewpoint it doesn't matter how many guns you own.
Anyways, Battle of Athens linksies because it is a REALLY cool story: http://www.constitution.org/mil/tn/batathen.htm
The cost of feathers has risen, even down is up!