@jayeless Great post! There's a lot of room for experimentation in this problem space. Fraidycat is a feed reader with an interesting approach:

There is no news feed. Rather than showing you a massive inbox of new posts to sort through, you see a list of recently active individuals. No one can noisily take over this page, since every follow has a summary that takes up a mere two lines.

And speaking about algorithms, I absolutely love how transparent Bear is on their Discovery Feed. Scroll to the bottom to find the algorithm and explanation: Score = log10(U) + (S / D * 8600).