Ok now take this whole bunch of salt, because I have no idea what Diaspora is planning, but another model might be more like p2p. So there are no accounts with

Ok now take this whole bunch of salt, because I have no idea what Diaspora is planning, but another model might be more like p2p. So there are no accounts with Awesomea or Crapula. Instead you have the diaspora software running on your own machine. Now Awesomea and Crapula have some social aspects on their site - for instance they want to send an update to your friends. So Awesomea and Crapula sends a request to your ip on the Diaspora port which includes the update message. Its now up to your computer to distribute that message to your friends, and Awesomea and Crapula have no idea who those people are. Of course you'd probably want the diaspora software hosted externally, but the model could still mostly be the same. Now if Awesomea or Crapula need to compute something using private data, I don't know what happens, perhaps they can provide logic to be run in a diaspora sandbox somehow.