To me, they're building a platform for journalism/media. They might be in the nascent stage where LinkBait is a dominant strategy, but I'd bet that high-quality journalism will become an increasingly integral part of BuzzFeed's business as it matures.
Quality journalism doesn't pay in a dollars in to dollars out basis. A carefully-researched article that takes a week-long trip to the Congo to write will get no more and possibly fewer clicks than "Ten Amazing Shark Facts That Will Make You Shit Your Pants" that takes twenty minutes on wikipedia.
They have more in-depth content but I imagine it's a tiny part of their overall traffic: http://www.buzzfeed.com/longform