Earlier quoted context omitted.
It's such an extremely simple litmus test: if it breaks the back button of the browser, it's the wrong design. The closest thing to an exception being cases where one needs to be logged in to see a page, or when links are consciously invalidated for some other reason. And even then the website/webapp should still just signal this to the user without a bazillion redirects.
Not necessarily: I do not want to click back 30 times to get out of your slideshow and back to my Google results. Thank you.
Try right-clicking the back button. Or complain to your browser maker -- they're responsible for its behaviour.