Note this is a fairly longstanding vector (offshoot?) of Reddit; it's been going on for at least a few years, and was featured on Reddit's blog in August 2012: http://blog.reddit.com/2012/08/university-of-reddit-explore-...

Here are the previous Hacker News discussions about it:

https://news.ycombinator.com/item?id=5366423

https://news.ycombinator.com/item?id=4409219

https://news.ycombinator.com/item?id=1479143