Twitter is, by most conventional metrics, considerably less popular than Facebook and arguably growing more slowly to boot. But one place where Twitter is absolutely crushing Facebook is in hip-hop lyrics, as measured by Rap Genius' amazing new Rap Stats tool.
Given the normal dynamics of cultural appropriation and so forth, this is arguably a key bullish indicator for Twitter. It's way behind right now, but considerably more popular on the cultural cutting edge. But of course that's just a hypothesis. What we really need is someone at one of the investment banks or quant funds to really crunch the numbers and see if rap lyrics are a leading indicator for consumer products.