There are many sites out there (e.g blogs, e-commerce, wikis, forums, etc.) which provide member areas by allowing members to login.
I think it would be really cool if piwik had functionality to check if the user is logged into the site (maybe by checking the session for userid or something) than using the data for reports.
You could provide graphs on the ‘most active users’, you could also match up the username to the ‘visitor log /real time’ .
I think this would be really neat, what do you think?