Facebook is fully entitled to enforce edgerank. People consume content differently on FB than say twitter. Since twitter is more of a firehouse, its OK to simply sort by date since newness has much more value in that ecosystem. This is socially acknowledged given that tweets are firstly public. In contrast Facebook presents itself as a local social network. As such, your relationships on FB carry more weight. Social pressure nudges us to 'friend' mere acquaintances and 'like' things that are mildly amusing. You're expected to acknowledge important news in your social circles. Edgerank reinforces this behavior. If something is deemed 'like'able by your 'friends' you're encouraged to also like it, both by the algorithm and social influences, thus perpetuating the cycle to your own network.

Brands don't fit into this picture. You don't 'like' a picture of coca cola from a crazy party at mcdonalds' house. Your interactions on the comments of posts by a brand are probably one way, and with predominantly strangers. The rest of your personal network is unrelated.

Thus, sponsored posts work against edge rank. There are two big examples of sponsored posts. First is say, promoting a personal story or life event (it's a boy!). Second is corporate to consumer say, Best Buy is having a huge sale on something. In the first case if a story is truly important it would have been picked up by the algorithm and social forces alike. In the second, most people don't believe corporations are people, and their social interactions with them are typically unwelcome to their personal network. There's no social pressure to like a picture of Jones soda's new flavor as opposed to Jenny's new baby.

All in all, I think mark is right for the wrong reasons. FB's business model runs counter to its primary product offering. They're still experimenting and I hope they end up with something that makes sense to a social network.