The heavyweight personalization that social networks do either through something like the follow graph on Twitter or through more algorithmic approach on Facebook is designed to give people the stuff that they want. What we're focused on is giving people stuff that they think is worth sharing with other people. We want the stories we're doing to have the biggest possible impact. So if we do personalization, it would be more of a personalization about what you’re most likely to share or discuss with your friends.
That's Jonah Peretti on what type of personalization Buzzfeed focuses on, emphasis mine on what is a subtle but important focusing distinction for the service.
In the traditional news bundle, say in old school print newspapers, the mix of serious versus entertaining content was weighted much more to the former. Now that technology has allowed the creation of more personalized bundles of information, sites like Buzzfeed and the social networks like Facebook and Twitter are showing us people's natural preference in the mix of heavy versus light, and it turns out that ratio is much more weighted towards the fun.
As in the newspaper days, the entertaining content still subsidizes, to a large extent, the serious journalism. Buzzfeed is starting to do some original reporting, but more likely than not it's ad revenue from listicles and the more “frivolous” content that will pick up the tab for both. Plus ça change.