I use incognito mode quite often when I'm demonstrating how to use a web app or website that requires my username and password. I also use it when I want to show people what a shared or published Google Document looks like when you're not signed into a Google Account. In both cases opening a new browser in incognito mode saves me the hassle of signing out of an account when I know that I'm going to be back into it in a few minutes. Incognito mode thinks that I'm a new user and doesn't have my saved usernames and passwords so I'm able to show sites and documents as they appear when I'm not signed into them.
