Use incognito mode for search that you don't want showing up in your search ads or history, looking at girly sites(Oprah etc), looking up cat videos(if you live with a dog person), and perusing advanced magnetic/electric research that might get you a call from some unsavory types. Also good for determining if your friend's glee club is actually a terrorist organization.
Just remember that if you close the tab of that obscure but hilarious cat video, it'll disappear into the void. You can't reopen it with ctrl + shift + T. Although if you use a router it will still keep logs of your activity. I ain't afraid of no ghosts.