The Reddit team In December 2011, Reddit served just over 2 billion pageviews to almost 35 million visitors, and each visitor spent an average of 16 minutes on the site.

What does it do so well to keep the site so engaging?

The answer is that Reddit doesn't tell its users what to care about.

It lets users customize their front page with whatever niche or mainstream topics they want.

If a topic isn't available to subscribe to, Reddit makes it very easy for users to create a topic page, or "subreddit."

Handing over topic creation to users helps keep Reddit ahead of the curve on what's going to be the thing on the Internet everyone wants to talk about next, be it Occupy Wall Street, zombies, or SOPA.

Lots of sites have this type of functionality, of course. The genius of Reddit is that it's easily implemented.

How easily?