> With retroshare all resources are gone if you delete those, with Freenet & GNUnet you simply can't delete anything.

Sure, that's true and the advantage of Freenet and GNUnet. The flip side of the caching is of course that this comes at a cost: It takes a lot more resources to have this kind of redundancy.

RetroShare btw does let you download files anonymously from friends-of-friends etc. if the "owner" agrees to it. (You only have to know your immediate friends.)