It is a really interesting topic to discuss. It seems like we need to have a tool/framework on the browser side which allows advanced users to redesign the layout of a web-site. It is pretty clear right now that Twitter has different groups of users and it is clear to me that Twitter should have different designs for them. Even in that post we could see people who "consume" timeline in a different way :)

IMHO Twitter/Facebook/Google+ should have Rich API and a default client but the user should be able to select implementation from different companies. (Similar to a search engine in the browser)

So, twitter has a 100k API token limit, but would that really be a constraint for such a project?