This paper looks at the impact of commercial pressures upon common lands. Its main task is to identify the factors which make local possession of the commons vulnerable to involuntary loss in the face of such pressures. As preface, it elaborates what constitutes the commons. A sharply accelerating rise is currently being seen in large-scale land acquisitions for the purposes of commercial food and biofuels production. With exceptions, these acquisitions are being made in developing economies where the majority of the local populations depend upon land use for their livelihoods, signalling likely competition for resources. The prominence of foreign buyers, including governments, has been internationally observed, although local host country investors are also active land buyers. Sub-Saharan Africa is the main location for acquisitions, with around 20 million hectares already formally acquired since 2007. For this reason among others, including the striking poverty of the sub-continent and the immensity of its commons resources, sub-Saharan Africa is the paper's principal focus of analysis.