As someone partial to the concept of memetics and Universal Darwinism, I happen to like when biological/Darwinian principles are applied to higher-level concepts. That being said, there may be ways to differ with the article's analysis even within the biological analogy: it's possible that Facebook and its users have a symbiotic relationship (social features in exchange for traffic/attention/ad impressions) in which case the user base may continue to stay with the site until an even more advantageous website comes along.