This is a tough issue, and one for which there's very little agreement event amongst self-described revolutionaries. The problem is tht if you look at the history of revolutionary movements, you find that violent revolts often make the situation worse, not better.

The anarchists in the 19th century, for instance, embraced a tactic called "propaganda of the deed", where they would capture army bases and radio stations and so on. Sometimes people ended up dead. As the word of this tactic spread, more rabid types started assassinating heads of state and industry, hoping this would spur the starving masses into out-right revolt.

It had the opposite effect, turning people off. They saw images of bloodshed in the papers, were repulsed, and tried to dissasociate themselves from the very people who were trying to help them most, the people who organized the campaigns against child labor and so on. The corporate press is highly skilled at ignoring, downplaying or turning upside down massive institutionalized violence (wage-slavery, war etc.) while trumping up individual murder cases, even when the person murdered is absolute filth. We recoil in horror at the death of JFK, but shrug our shoulders at the millions he was rensponsible for killing in South East Asia.

I have no doubt that were Bush taken out, liberals would be all over the place weeping and begging for "unity".

Anyway, the anarchist movement abandoned the "propaganda of the deed" and focussed their efforts at education, union organizing, international solidarity movements, local farming and so on. A century later, it is clear that these efforts have only been marginally effective. Indeed, for every gain there as been ten or twelves losses.

There are still groups called "insurrectionary" anarchists (like the black bloc), who are hell-bent on pushing the envelope, but even these hardcore types shy away from the kind of actions we just witnessed in Mexico, perhaps because they're all too aware of the "bomb-throwing anarchist" caricature. They're willing to engage in property damage but they don't go all the way -- and perhaps they shouldn't. Yet.

There are also lots of examples of violent revolutionary movements in Latin America that failed where non-violent civil disobedience won. Dozens of them in fact. Despots were strengthened by violent assaults (which are their forte, after all) but made impmotent by mass non-violent civil disobedience.

However, you would be hard-pressed to find a single Latin American country for which the mass of the populace has any control over the matters that most effect their lives; this is one of the problems with governments of any kind, be they marxist or liberal democracy like the US.

Overthrow the current tyrants, and a new batch will be there to take their place. Unless, that is, we change our entire paradigm and get rid of the concept of huge governments all together, devolving power to local communities and federating horizontally.

There's some interesting debates beween anarchists on this subject, between (for instance) people like Ward Churchill and Michael Albert.

It's a very tough issue, and no one really has the answers. Sometimes, small rebellious actions act as force multipliers and change history for othe better. Othertimes, they are ruthlessly suppressed by the state and actually increase repression.

The good news: there will come a time when enough is enough, and no army in the world will be able to prevent progress.