Finally got around to reading this analysis by Ben Thompson. tldr: it’s one of those “it’s about the value of the data!” arguments. The biggest difference, which the author correctly touches on early is that the user base is simply a lot smaller than others in the cohort. This suggests there’s a lack of mass appeal for their flavor of network.
Indeed, I would argue that what makes Twitter the company valuable is not Twitter the app or 140 characters or @names or anything else having to do with the product: rather, it’s the interest graph that is nearly priceless. More specifically, it is Twitter identities and the understanding that can be gleaned from how those identities are used and how they interact that matters.