Hey, this is cool, but I would suggest that taking ecib's train of thought to the extreme is the wrong way to use it. That is, don't use this feature to cull who you follow down to who you've shared most often; that way lies homogeneity and black holes and red-on-yellow-kill-a-fellow snakes. EDIT: not to suggest it's a bad feature by any means; actually I quite like it.
I think it'd be cool for discovery purposes. If you are lurking through the global posts and see some slightly familiar usernames, you could toggle over them and see if you have shared anything by them and what it was you shared. It would be nice if on any page when you scrolled over the name and the number came up, you could scroll over the number and click on it and be taken to the list of content you've shared of theirs.
For me, that is a secondary function. The colored follow/not-follow name indicators create a negative incentive to unfollowing people at any rate, much like other some social networks. Is it lame to feel guilt over unfollowing someone? Pretty much, but human psychology is what it is.