"common groups of users encrypt data for each other with each others keys"

I agree, but I think this can quickly lead to massive multiplication of data without careful cryptographic gymnastics. It puts more pressure on the application devs to do it right or more pressure on the network in terms of data if you don't.

"Sure you can still leak your private key like you can leak an SSH key today."

If I leak an SSH key, I can revoke it and only data that attackers have already grabbed is out. In the described paradigm, everything is already out to everyone. It is all or nothing. That might not be a difference from a theoretical point of view, but in practice it is.

MaidSafe is very interesting, thank you! It seems like more of a shared cloud, which is halfway between present cloud computing and the completely distributed utopia described in the article. It solves pretty much all of these issues, with the cost of being a less-centralized network rather than a fully distributed network. Awesome work, I hope they succeed!