An interesting article about land grabs in The Economist:
Land grabs have been strikingly popular. Preliminary research by the International Land Coalition, a non-governmental organisation, reckons almost 80m hectares have been subject to some sort of negotiation with a foreign investor, more than half in Africa (see chart). This estimate is far higher than a previous one, by the World Bank, which last year said that foreign investors had expressed interest in 57m hectares. It is higher still than one by the International Food Policy Research Institute (IFPRI) which put the figure in a 2009 study at 15m-20m hectares. It would be wrong to draw a line between these numbers so as to conclude that land deals have grown fourfold. Since most are secret, knowing what to count is difficult, and the figures refer to different periods.
Note that when land deals are initially proposed four main benefit0s are offered to the host countries (apart from the benefits to the deal seeker): more jobs, new technology, better infrastructure and extra tax revenues. None of these promises seems to have been fulfilled according to the article.
So why are land deals popular? That is surprisingly easy to answer: strong demand and willing suppliers. The big investors tend to be capital-exporting countries with large worries about feeding their own people. Their confidence in world markets has been shaken by two food-price spikes in four years. So they have sought to guarantee food supplies by buying farmland abroad. China is by far the largest investor, buying or leasing twice as much as anyone else.
Here is info about conference related to land grabbing and related papers.