Ben Thompson wrote a characteristically astute analysis of How Facebook Squashed Twitter. The whole essay is worth reading, but it’s this part in particular that stood out for me:

Facebook has developed its own interest graph that is far more powerful and effective and easier-to-use than Twitter’s ever was. Yes, Twitter still owns niches like NBA Twitter, and news hounds like myself (and most of you reading this article) will continue to find it essential, but for nearly everyone else in the world it is Facebook that is the first thing people check, not just in the morning but in all of the empty spaces of their lives. In short, it’s not simply that Twitter needs to convince users to give the service a second-chance, something that is already far more difficult than getting users to sign up for the first time; it’s that even if the service magically had the perfect on-boarding experience leading to the perfect algorithmically-driven feed, it’s not clear why the users it needs would bother looking up from their Facebook feeds.

This is a perfect example of The forces at work when choosing a product. In short, the progress-making forces that might push people from Facebook to Twitter are not nearly as strong as the progress-hindering forces that keep them on happily on the “good enough” that is Facebook.