The biggest problem with this mindset is proportionality at the moment - bank safe deposit boxes have much more public awareness than these services, and have thus gained wider use (and acceptance).
Here's a thought...
Put on your foil hat for a second. Let's say you were a government and you wanted your citizens not to use systems like Tor and FreeNet. Wouldn't flooding them with extremely disturbing porn be a great way to make sure these systems weren't used by anyone except CP wankers? Wouldn't it be a great way to get people to go along with outlawing them?
This is a technical problem. When you think about it like that, it becomes obvious that this is a vulnerability in the security/crypto sense. I'd state the problem this way: these networks are trivially vulnerable to a particularly devastating social engineering spam attack that renders the network virtually unusable by most people. Call it a social DOS attack.
Edit: I believe I can state the problem succinctly:
Design a darknet/freenet network that is anonymous, uncensorable, and yet is not trivially vulnerable to social engineering DOS attack.
Hard problem. Hard equals interesting.
Personally, I've spent quiet some time on the .onion network and never been ambushed by child porn. Don't you think your problem is solved on the .onion network the same way it is on the clearnet: with moderation on a website-by-website basis?
What I'm saying here is that there's an interesting unsolved problem and that this problem might be the thing that's blocking the adoption of these technologies.
It's also a critical mass problem. I don't think you could run that sort of attack against the Internet because it has over a billion users. Once the network reaches a certain mass, it becomes far less of a problem. The problem is that CP-wankers (and possibly attackers) instantly colonize darknets, rendering them quickly polluted before they have a chance to escape their nascent phase. Like I said in another post: you could apply game theory here.
The specific issue with these networks is proportion of use: they get co-opted so early by bad uses that they never get a chance to show their legitimate side.
I'm not going to make a blanket statement that this is a good or a bad thing, since it largely depends on what's in there (the technology itself is neutral); and some jurisdictions might define as depraved indifference (minimally) or facilitation (maximally) should the contents be illegal.
Also I can easily foresee that being unable to trace the provenence of data stored on one's node could put one in a difficult position to assert it isn't one's own, when possession is usually all that is needed for criminal liability.
The banker can cover the ownership case, and hence his backside.
As far as public/private goes, it seems this network from what I read, maintains an opacity shield with regards to contents, but is peer-to-peer storage. So in that regard, neither the safe deposit box nor the storage network are "publicizing" anything, per say.
But in this case we know they are swapping pictures of child abuse, we just don't know who they are. The problem is the inverse.
But more-over, even if you investigated Tor exit-node traffic you can't know if any porn you might see was actually being traded or merely continually transferred by repressive regimes to have an excuse to ban anonymity providing services.
You suspect a lot, and have reached some conclusions, but you don't know what it is, let alone who if anyone is doing it.