Interesting that they should mention democracy. The About page unapologetically calls it meritocracy, which is honest and accurate.
Like other systems available online (for instance, Podcastalley and, obviously, Digg), the way users rate content is by adding their “vote” to as many items as they want. That in itself is an interesting concept. The only thing the user needs to say is “I like these ones,” without any need to compare specifically. It’s not competitive in a strict sense, yet it’s a rating system. So it’s more of a popularity contest than a true meritocracy. It’s a bit like the “two thumbs up” statement on so many movies in that it doesn’t require much from the reviewer yet it’s a way to assign positive value. Because some reviewers acquire social capital, their choices will become popular which adds a positive feedback loop to the system.
Of course, people can post comments, which is the very basis of the type of contact and communication proposed by the venerable (!) Slashdot as well as the whole blogging community.
The other part which is quite important is that tags are applied to content which makes for community-created bottom-up classification (unlike strict taxonomies). Many online systems have this (say, Technorati). Of course, classification may be unreliable at first and tags may seem idiosyncratic. But the tagging system itself seems to work well on average. Good way to observe cultural schemes being created.