One of the things I've been asked about recently is why Facebook's product releases have been much more experimental and diverse than Twitter's. And the thing that's stuck out to me most is how both companies seem to view what they're doing. Facebook views their mission to help people connect. So, as a Facebook designer, there is an incredible amount of leeway one can take, as there are many different ways to help people connect. Twitter, on the other hand, is a bit more oblique. Their mission is to allow people to send out public messages of 140 characters or less. With that definition, there really isn't a lot of room for innovation: the product has already been built. With that mission, there really isn't a whole lot of places to go.
I think this gets at something fundamental that we often ignore in the tech scene: there is a fundamental difference between having a conceptually simple product, and a simple product to use. Yes, Facebook's product is incredibly complex - I remember a friend turning to me and saying, "there is no way any designer would have designed and okay'ed that homepage!" But that's not true - if it's true that Facebook thinks of themselves as building a toolkit for social connection, then that design absolutely makes sense. Users come to the site, and they seem to have some sense of how to use it and what to do there, driven by the very clear goal that they use Facebook for connecting to their friends. Twitter, on the other hand, has a comparatively simple product in terms of usage. But conceptually? It's not only completely obscured, it seems to have multiple use cases as well! I've got to imagine thousands of commentaries have been written on what exactly Twitter is and how you should use it. One wonders if Twitter's lack of complexity has more to do with a fear of toppling any one of these conceptual use cases users have, both by limiting use through product, but also committing to any of these use cases from an organizational perspective.
It seems like conceptual simplicity transforms flurries of links and navigation into a variety of affordances. I'd argue that many of us simply cannot use a tool that doesn't have these kind of affordances subtly suggesting what we could do next. It is easy to know what everything does on a Twitter page, but it's difficult to figure out what you should be doing.