This could be very useful - it's a purely client-side solution to remember which account you used to log in to a site the last time and multiplex accounts. My

This could be very useful - it's a purely client-side solution to remember which account you used to log in to a site the last time and multiplex accounts. My only initial complaint is that the UI is ugly and confusing, and it doesn't seem like they want you to customize the UI (especially the post-sign-up UI). There's nothing stopping you from forking AccountChooser and running your own implementation, but it seems like much of the potential value is getting users accustomed to a common sign-in UI.