Social News Site // Digg.com

Digg.com is a social news site. Everyone can submit stories (ranging from keyboard cat tributes to election debates, with a lot of web/tech/science stuff in between). People can vote on stories, which is called 'to digg'. Popular stories reach the front page. Negative votes can be placed as well. This is called 'to bury'. Without an account, you can't interact, but you can read the articles (ie skim the most popular stories).

(Most) Popular, upcoming, etc
There's various algorithms that determine which article is placed in which list. There's lists with popular stories, but also more personalized lists for those that are logged in. With an account, you can also follow others (ie your friends or interesting people), so that their stories and diggs are brought to your attention.

Community and Commenting
There's a lively community that submits, digs and comments to stories. The fact that you can easily and anonymously bury comments of others is a good weapon against spam. Be warned though that your comments can and will be buried also for other, often unknown, reasons.

Spam
Only a few days active on the site I already got a bunch of followers. Most were newly created accounts that had already submitted a bunch of articles all originating from the same website. Some cases were obviously pure spam, others were less clear.

Background
Digg.com was founded by Kevin Rose. He's now left the company after a roll out of a new (game changing) version caused a lot of fuzz, partially due to technical difficulties. This was a good example of how the foundation of any social site (the visitors) can all of a sudden collapse or even turn against it. Since then, the site seems to have picked up, but its foundations are no longer as sturdy as they used to be. Still, the site is at Alexa rank 143 world wide!