Yeah, I'm sure those hundreds of millions of people will be able to sustain themselves on that fraction of an acre of land. We've moved beyond the agrarian model. With the amount of people on earth it's not possible for everyone to be a farmer.
Of course not, but the people who are farmers will be able to produce enough food for the people who aren't. In the model we have now, what usually ends up happening is simply that no one produces food at all. Land that was previously used to produce food for natives is converted to produce, say, flowers for the American market. What's more, where there were hundreds of people working on that land originally, it's all machinized, so nearly all those people end up out of a job.

Simply converting the land back to its original use would solve quite a lot of the problem.

I agree, globalization isn't the greatest thing, but it's debatable if things would be that much better if that exploitation didn't exist. If foreign government isn't willing to protect its citizens from unfair wages and work environments, who's to say they would do anything to benefit the country if U.S. economic influence didn't exist?
My point is that on occasion, they have actually done things to hurt the vast majority of their citizens thanks to the influence of multinational corporations. For instance, raising property taxes to an insane level in order to force natives off their land; there are documented cases of this happening in southeastern Mexico.

So the state should have the right to tell you when you've made enough money and when you've acquired enough possessions?
Pretty much. That money and those possessions always come at the expense of someone else. Look at it this way: America is a nation of people who consume and don't produce (by and large), so the Third World is an antimatter universe of people who produce and don't consume.

The capitalist model is founded on the assumption, based on Adam Smith's conception of the "Invisible Hand," that everyone, in maximizing their own self-interest, is maximizing the self-interest of the public as a whole as well. Unfortunately, this assumption is demonstrably untrue. Let us take the example of the tragedy of the commons. For those who are unfamiliar with it, there is a commonly owned land where everyone is allowed to graze cattle. In this scenario, it is in every farmer's self-interest to have as many cattle as they can, so they can raise as much milk as possible and make as much money as possible. Unfortunately, after a certain number of cattle graze on the land, they eat the grass down to its roots, and after a point, milk production actually goes down. It's still in everyone's self-interest to graze as many cattle as possible, though, so no cattle get removed, some probably get added, and the commons end up completely unusable for any grazing purposes whatsoever.

This can be extended to so many scenarios - overfishing of the ocean, the case of driving cars versus using public transportation, and I could go on. The only solution to these problems is when a coercive outside entity, necessarily the government, steps in and says, "Enough is enough." Naturally, there are plenty of cases where the government itself can be corrupt, and that is why I favour as much transparency as possible in government and as much civic awareness as possible in the population (which naturally requires a solid education, and thus implying a number of other things as well, but that's irrelevant really).