I feel like every new iteration of ways to find good content online: webrings, blogrolls, user upvoting/downvoting, giving everyone their own microblog to share interesting links, ML to learn your own preferences by your behavior - they all worked really well at first, but then eroded significantly once people figured out how to game them.

The economic incentive is overwhelming to corrupt these signals, either directly (link sharing schemes, upvote rings, bots to like your content) or indirectly (shaping your content itself to have the shape of what will be promoted, regardless of its quality).

What you almost want is to use any of these ideas and hope for it to catch on widely enough in your small niche to be useful, but not so much that it comes an optimization target.