Your own visits are being tracked by the stats program and Staff of course can access any blog.
Private blogs, which can be viewed only by users chosen by the administrator, now track the page views of all of their users. Traditionally we have omitted the views attributed to a blog’s own users because stats were meant to reflect the activity of the general public. However, this meant that private blogs had no useful stats reports. This change will be especially useful for private blogs that have many users. http://en.blog.wordpress.com/2011/08/18/watch-your-traffic-grow-with-sparklines/
Could someone please check that this blog is truly private.
Volunteers do not have backend access to blogs. I clicked your link and got the "protected blog" display I expected to see.
http://joniem.wordpress.com/ is marked private by its owner. You can confirm this simply by logging out of WordPress.com and approaching your blog while logged out like any stranger would do.