Forever is a mighty long time. Just ask Prince. But that's the lifespan that Quora thinks it scored by accepting $140 million in venture capital. According to Re/code, the Series C round values the 4-year-old, revenue-less Q&A site at $900 million, more than double the $400 million it was "worth" in 2012.

Quora, the question-and-answer site that convinced investors to part with a whopping $61 million, is notoriously unwilling to release any concrete data about its growth—preferring, instead to dole out vague vanity metrics. Maybe that's because its traffic is coming from outside the U.S.