2018/08/30: Removing content from a decentralized, content-addressed system is difficult to implement:
At the organizational level, who is the censor in a decentralized Web to whom the request to remove content is addressed, and who decides whether the request is valid? Facebook has a vast team of content moderators failing to purge deprecated content. Google has a whole organization handling DMCA takedown requests. How are their equivalents in the decentralized Web to be implemented and paid for?
At the technical level, it is close to impossible to prevent abuse of the mechanism for tracking down and deleting all copies of some named content the censors need to do their job. Or even a mechanism for just de-indexing it.
In the absence of mechanisms that enable censorship, it won't just be the incumbent platforms trying to kill our new, small companies, it will be governments.
So the decentralized Web faces four major problems. Without solutions to all four, it won't come close to my 1% definition of success. No-one has good ideas for solutions to any of them. But, at least at the recent Decentralized Web Summit, some people were drawing attention to each of them.