Ghostery does what the user tells it to do. If you are seeing unblocked trackers, most likely, its because we've added new trackers and you didn't select "block" by default for the new trackers when the list gets updated. You can change this preference by going into Ghostery options, Advanced, and review the "auto-update" section.
And heres a full explanation as to what Evidon gets and what it does with it: http://purplebox.ghostery.com/?p=1016023438