Consider adding to the Anyone Can Censor sharing site a seemingly ridiculously draconian feature that any published URL to content on the sharing site that the sharing site owner can find will have the linked content censored, killing the link. Finding publicly published URLs to a site can be done with a search engine.
At first glance, it seems the site owner is defeating the popularity of his or her own service. However, such a policy or feature might help promote the growth of trust networks, so that URLs to content are only disseminated along trusted covert paths. Those who want to censor content can typically find it only when published.
URL link shorteners easily defeat this, but that might be OK.