It is really hard to enumerate Freenet clients if they run in darknet mode. It is trivial to enumerate all I2P clients though. It is really hard to enumerate Tor clients because of entry guards and bridges and obfsproxy. Freenet is really unique because it aims to provide plausible deniability in addition to anonymity. I2P has a little bit of plausible deniability from internal attackers (because essentially all clients route for each other, and there are variable length paths), but not external attackers. Tor on the other hand is focused entirely on anonymity, it has pretty much no plausible deniability at all except for *maybe* if you run as an exit node and claim that connections to the clearnet came from Tor users (and even this will not protect you from an external attacker). If an attacker watches your Tor entry guard and the destination you surf to, you are pretty much fucked. If your direct freenet peers watch an illegal file being routed to you, they still cannot easily prove that you actually requested the file, for all they know you are just routing it for somebody else like they are. If they see you insert an illegal file into the network, they don't know if you are the person who originally published the file or if you are just routing on an inserted file like they are. The plausible deniability of Freenet is what makes it so much more robust than Tor. But like you mentioned, Freenet is very different from Tor and I2P. You don't run a normal server and anonymize it with Freenet, rather all of the nodes make some of their hard drive space available and content is hosted redundantly distributed throughout the network. This means running php forums etc on Freenet is impossible. However I do think a site like SR could operate on Freenet, it would just need to use custom client side software designed to work with Freenet. Just like there are Freenet specific software packages for forums, E-mail, etc.