It looks like at one point, mozilla attempted to solve this with their context graph project as well as their acquisition of pocket. However, it does look like it has all the hallmarks of a technological solution to a societal problem. Solving the adverserial aspects as well as ethical concerns would require nothing short of a rethinking of how we use the web.
https://medium.com/firefox-context-graph/context-graph-its-t...
I've always been curious whether any search engine tries to index the "disconnected web" by just war-dialing domains/IPs like this.
> To some degree, DNS is a broadcast system for discovery.
Sadly, there's no real way to build a "DNS spider." You could if you could send DNS AXFR queries for arbitrary zones; but DNS servers mostly don't respond to these without authentication.
The problem with "social media curation" as a qualifier could be interpreted as "a human is involved." Pretty much all forms of discovery, internet or not, requires either search or a human involved. Some services of course have broadcast mechanisms for curating an index but that's about the only exception I can think of for discovery that breaks away from these two qualifiers. To some degree, DNS is a broadcast system for discovery.