It's no secret that Twitter is now putting others' favorites into your timeline, but the actual trigger for those appearances has remained a mystery. Is it purely random? Keyword-based? As it turns out, it's more like a slot machine. The company's Dick Costolo has revealed that those favorites appear when you pull to refresh twice, and there aren't any new tweets to show. Twitter is simply trying to respond to your insatiable demand for updates, Costolo says. In other words, the social network would rather give you some recycled tweets than leave you hanging.