Diaspora pods vs p2p

[Maarten Vergouwe]

Is there a specific reason why Diaspora* is not based on a peer-to-peer network instead of a network of hubs (pods)? 

I am walking around with the idea to create a peer-to-peer social network and stumbled upon Diaspora*, which is already much better than Facebook, but still has the problem that data is stored somewhere else. I'm wondering if P2P has ever been an option, if so, why it has been abandoned