Maybe there is already a good source of experts on Quora or something. Or start a new site where experts are invited.
Yeah I think this would be a great idea. If you had the capture ability of sci-hub with the invite ability of quora to get experts to critic papers. Then add on-top of that some simple blog features like top highlight, sharing, subscribe to citation links, and comment/discussion (that matches HN's no counter productive comments/etc).
The large obstacle would be paywalls - like sci-hub; any attractive paper would be illegal to have on the service; if you simply pulled from pre-prints (arxiv; plos pre-print, etc..) you will probably lose academic disciplines that do not value these services (biology primarily comes to mind). On the other hand, CS would probably embrace it as a complement to their conference publishing culture.
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I like pre-print services, and I wish they would go one step further and allow people to comment/critic the paper. This way, when you find a paper, you could see all associated thoughts and join the conversation. The really powerful idea behind pre-prints is that it would speed up academic publishing, by eliminating the ~6 month publication time.
The only problem with pre-prints (currently) is they are not widely accepted for academic tenure. With academic publishing being a multi-billion dollar industry, I'm kind of surprised there are not more tech startups working on this issue.