Steps to make a Facebook Killer
ashishlive.blogspot.com
ashishlive.blogspot.com
The advantage of this would be that non-technical users would have a very FB-like experience, while more technical users could modify the app to suit their own preferences, and then share the app source with others.
The important thing would be to keep a standard api so that the different app versions could communicate.
And finally, it assumes that finding a better solution will 'kill' Facebook, whereas I think it's much more likely to be taken down by a site that knows how to market.
So why make a Facebook-killer?