If you enable CKEditor (with CKFinder) and not set a private file folder, the images will be uploaded to the public files path, and be visible to all. But if you set an explicit private file folder (second input in admin/config/media/file-system), the files are uploaded to the private folder. Although this may be handy in some cases, in Drupal 7, a .htaccess in the private folder disables all access to it, basically removing all access to these files.
I can enable access to all private files by removing the .htaccess, but there are other files in the private directory that I don't want to share. I think that the CKEditor should either place all files always in the public path, or it should output the uploaded images to the users via a callback. And there should be options to which users what is available, because why bother putting it in the private folder instead of the public folder otherwise?