When I have a 1000+ folder, I tend to hesitate before clicking “Mark all as read”, because I’m afraid I’m missing something very important. If I was able to sort the reader items by the number of likes plus the number of times it has been shared, I would check the hottest items before trashing all the others, and I would feel safer.
Please Google: do it.
Actually, thinking about it, some precautions are needed. Each feed owner could create many accounts just to share and like their own entries and take them to the top… A possible solution could be to sort items by likes from people you follow, since it could also encourage to increase the number of contacts.