It used to be so easy to remove items from the sidebar of OS X Finder windows. You’d simply click, drag, and poof! The offending item would disappear like a well-heeled Dock icon in search of greater opportunity in the world.
Today, however (and for quite some time, really) you can’t just click and drag the sidebar items away without giving it a little more thought. That’s where this handy keyboard shortcut comes in.
Sure, you could use the right-click (Control-click or two-finger click on a trackpad) to bring up a contextual menu, but where’s the fun in that?
Have you tried to get rid of an application or document from the Dock after an upgrade to Mountain Lion? Before now, it was a simple drag and release: click on the offending icon, drag it away from the Dock, and let go. The little “poof” cloud would appear and the icon would be gone from the Dock. New OS X users would freak out, crying, “You got rid of my app!” and I would laugh. Also, I would show them where the actual app was, and how to put the icon back in the Dock, as the icon is simply a pointer to the real app. But I digress.
In Mac OS X Mountain Lion, this doesn’t work in quite the same way anymore. Try to click, drag, and release just ends up with the icon speeding back to its previous place in the Dock. You want to get rid of it? You have to learn a new, subtly different behavior.