I can see academic message boards pre-Empire. Actually, I can see them pre-Clone Wars. I imagine that a lot of the censorship that went into the Holonet during the Empire actually started during the war as a means of containing Separatist propaganda, that is to say, dissent.

I know there's a scene in the Clone Wars cartoon where Ventress is looking through a posting of bounties at a bar, so I don't think it's just a Cowboy Bebop thing. It was more a database and less a show though. Thanks for pointing it out though, because I'm pretty sure it's the only time we actually see someone searching the Holonet on screen.

I am so with you on there being a Dark Holonet both for criminal activity and Rebel activity. It's the only thing that really makes sense when it comes to coordinating effort. They just don't seem like they'd be as ubiquitous or universally accessible as our social media, especially since the Empire probably would have been trying to track and crack down on users. I bet social media bloomed in the New Republic though, or at least those academic message boards came back up.