Plus, their layout is a mish-mash of content types. It's a jungle.
They've struck some secret sweetheart deals with newspaper companies to get their buttons on sites like CNN. I am assuming they were deals because there's no reason Mixx belongs in the same breath as some of the other sites with buttons on these sites. Mixx has backing from newspaper companies hoping to get in on the social news scene, which probably helped. And it's founders come out of the newspaper advertising scene.
You've got to get people who want to "hang out" together. Give them some shared purpose. And, above all, add value.
I think some of the sports news sites have found a solid formula by taking it a step beyond just "social news" into creating an actual network of sites that get just a bit of extra push on their site. This helps the social news site brand itself based on the quality of the sites in its network, and it also gives it a bunch of go-to friends to lean on for good stories, comments and the like.
Mix has none of these things. It's a generic place to submit stories.
And honestly, if it wasn't for Diggnation, the Kevin Rose saga and the "lineage" of Digg, that site would be in the same boat.
And without YCombinator, Paul Graham and his ethos, I think Reddit would as well. These sites had stories and solid tech that resonated with the first waves of users that got them going.
What's Mixx's story?
When it launched, I think there was some speculation that the Mixx folks thought they could pull away enough Diggers to get just big enough to be useful/profitable.
What's their story?
mixx is a top 1000 site in Alexa.
Compete measures only American audience.