I think your disappointment may be related to your expectations regarding what decentralized systems can or should do. You want centralized-level safeguards on a decentralized platform. Is this feasible? I don't think so without sacrificing decentralization.
data is encrypted
Yeah that's what I suspect but if your followers can decrypt the content, then they can also pass the decryption keys to others (?)
It's very feasible, and particularly on Synereo which has composability as a core design principle. Synereo is going to be a Social Computer, which means it can be programmed in any way we want to program it, using "Social Contracts" which is basically like smart contracts but for the social computer.
I setup the docker node to play around with, I'm still reading up on it and rholang etc. But it looks really interesting with the composability aspect as you put it. Might be able to replace or incorporate some other dApps like storj etc. So you can create contracts to rent extra storage space or cpu time and so on. Seems extremely open ended with what you could do.
I think thats actually solvable.
You could you have two keys? Your followers get a key and when viewing the content a positive check for the user key + follower key allows a third (stored) key to be added to the transaction signing.
Or perhaps just a check on user key + user is follower would work. This is just spit-balling. But i dont see an issue with multi-key signing to decrypt. It would however have several other downsides like usability, reduced public content (network effect), more difficult third-party app integration. Etc etc.
But the idea of encrypting content to be only viewable by some whitelist of users seems possible
Sort of, until your "private" content gets leaked or reposted somewhere. If you have a lot of followers you won't have any idea who did it either.
Not only could I encrypt it to a whitelist of users, I could encrypt some content with ABE, (attribute based encryption) so only users who have a certain reputation quantified on the blockchain can access it.