Torfi Frans Ãlafsson is Senior Producer at CCP Games, the makers of EVE Online. He was kind enough to say a few words about the upcoming Tyrannis expansion, which features the development and control of entire planets.
You can build infrastructure and interact with almost every planet in the game, regardless of whether someone has something there, already. The problem is that the planets are going to have limited resources. So if too many people are harvesting a planet at the same time, there will be diminishing returns.
Read more about it here.