Diaspora is bizarre, isn't it?
There are so many free-as-in-speech social networking software frameworks out there, what is one more? There is no way on earth that this is going to be even a blip on Facebook's radar.
Having said that, here's why this might be interesting.
If they get a combination of three things right :
a) the encryption / security / privacy
b) the user interface (so it's easy to install and administrate)
c) the hype, to get a critical mass of developers looking at it
If they do, then this could become an interesting basis of what you might call a "Virtual Private Intranet". A cheap way for a small distributed company to securely share profiles / discussions / news-tweets / files across the public internet.
Interestingly, although Facebook lets you create groups, it's not a great tool for say, people who like Dubstep,to set up a space where they can easily share their collections of mp3s with each other.
The trend is for social networks to get more private as they become more serious and more important. And there's plenty of room for growth in what you could call the "darknet" sector. (Criminals and cypherpunks have encrypted p2p sharing networks, but ordinary people and businesses still can't get them very easily.) So, if Diaspora
could make a cheap, easy-to-setup synthesis of Dropbox, LinkedIn and Twitter then they might have something interesting.
Of course, Ampify might get there first :-)