Why have readers log-in to a site? The meta widget gives the option. Jetpack's offers a WP single sign-on. Jetpack site stats configuration asks about what kind of registered users should be counted in page view counts (does that mean non registered users aren't counted at all?). Various plug-ins offer ways of people to register though other accounts such a facebook.
What is the purpose of having people log-in? How would you encourage them to do so, other than make them register to comment? Seems like an extra hoop to jump through.
Sorry if I put this in the wrong topic. It was the closest I could figure.