I'm a corner case. We both know that. But you build for the corners so that the middle is more stable. If I'm using "global" more than most, you should probably pay attention to me more than most. It means I've found more use for global than most, which means I'm predicting the future for everybody else. Default mod, here to help! Know what Reddit only started doing recently because it fucked with their made-up traffic numbers ('tis true: if you look at a paid traffic report for Reddit as opposed to Google Analytics, they're overestimating by 15-20x): Domain bans. I can already ignore domains. So can everybody else. You have the ability to track how many times a domain has been ignored, right? Set a threshold. Hell, set a threshold/alexa rank ratio - that way even if 20% of your users have huffingtonpost ignored, it'll still show up in Global because it's huge. ahametals? that threshold could be a little lower.Of course, looking at posts with more shares will help, but I don't think it would be too long before spammers start sharing with puppets.
Here's someone that hit the threshold fast: https://hubski.com/pub?id=146772