on the ideal case , most people don't force login_url because suppose for example, you've a login form above in the banner of your web app and when user stands in a specific page and enters his user/pass in login form , ...you don't want him to leave the current page right? moreover your web site users can't have bookmarks for protected pages because every time they hit the link they will be redirected to login page then back to the page you've specified [not the one they want] so bookmarking will not working.
in my previous post i'm referring to index because it's the default page after logging out Regards
