Mailchimp and others such KISSmetrics or SlideShare know that login, logout screenshots are some of corners of your site that are among the most visited. Many use them to alert about new features deployed in the applications, next webinar sessions, etc.
If you want to see it live, sign out of your Mailchimp account or go directly to their http://mailchimp.com/see-ya-later/url where you are redirected after your sign out.