I do think reddit have strong business model and generates more quality contents than Digg, for this I have backing from zdnet (http://blogs.zdnet.com/web2explorer/?p=99). And Ofcourse reddit is a very much success and my favorite. Look at this data going head-to-head with StumpleUpon (http://siteanalytics.compete.com/stumbleupon.com+reddit.com/...)
In terms of backing my argument, if you think reddit have gone far than the Digg I think you should look at the compete data (http://siteanalytics.compete.com/digg.com+reddit.com/?metric...) and this argument backing that, reddit isnt that viral(http://socialnewswatch.com/digg-versus-reddit/). My point is it could have been more viral with little more effort and more to it that no other startup came close to Reddit and Scribd (http://siteanalytics.compete.com/scribd.com+reddit.com+loopt...)
And I could very well turn this post off, if everybody favors with this.
There are a lot of great apps which fit this model, but they DO tend to be smaller in scope- The constraints of the model force uses to focus on their core feature offering, rather than adding everything under the sun, to appeal to as many users as humanly possible.
Why are people down-voting for asking a simple question? Is THAT what "25 karma" gives them?
This community seems to be getting a little too overcrowded with self-important downvoters. Sad, really. I used to like it here.
There is so incredibly much I could contribute here, but now I ask "why bother" if the community begins its inevitable slide (thanks, Tech Crunch!) into Diggland and Reddithood?
Everyone makes mistakes occasionally and gets downvoted (sometimes it's unfortunate but you can just get downvoted for expressing an unpopular opinion). But hopefully in the long run you bring positive value to the site and your comments are voted up more often than down.