[moxie]

Can you provide specific historical examples where censorship of federated protocols was difficult or impossible for technical reasons?

I can't see how there is anything technically difficult about it. To the extent that services aren't censored, it's usually either because they're not encrypted (so no reason to block them) or because they're too popular to get away with blocking.

[SamWhited]

As I said, it's not impossible, nor is it difficult for technical reasons, it's just more difficult because there's more stuff to block, and you'll never find every little server setup by a few activists to access the network. With proper encryption (or even basic TLS to the server) it also becomes difficult to do deep packet inspection (which is hard to do in the first place). The example I gave before also still stands: Look at the last time Egypt tried this. They attempted to block email and SMS temporarily and various activist groups just setup their own servers to get around it. Not every random user can do this of course, but it's important that at least some activists can.

[moxie]

"Various activist groups" setup their own SMS service?

If all you want is for a few hundred people to be able to communicate, you don't need a federated protocol, you just need a VPN. It is much easier to use a centralized service and access it with a VPN than to use a rotating set of hosts across successively blocked federated services. At least when the VPN gets blocked you don't have to rediscover your entire social network when you start using a new one.