Notice how for anyone who donates more than $5 they need to send them a CD with Diaspora on it. $25 gets them a t-shirt etc.
For 6k donors, they're going to spend ~$50-100k of the $200k they raised just meeting their commitments. Not to mention a huge amount of time dealing with the logistics.
Edit: Jesus, if you account for the fact that they promised 1 year hosted service, and 1 year phone support for anyone who donated more than $350, these guys are already underwater.