I stumbled across this behavior of the Unity desktop quite by accident (like so much else). Look in the lower left corner of the screen at the bottom of the launcher. Note how the lowest icons, starting with the Workspace Switcher, are stacked on top of one another, instead of lying flat as it they do from the Synaptic Package Manager up to Dash.
I discovered this behavior when re-starting the 12.04 VM. The VM screen tends to remain at the small default launch size, which is how I stumbled upon this behavior. It's an interesting solution to the problem that exists with 11.10. If the screen of Ubuntu 11.10 is small like this, then the lowest icons are simply covered with a shadow cast by the Trash Can. If you hover the mouse over the launcher then the icons will automatically scroll up, uncovering the covered icons.
The same behavior is observed with 12.04, except a little more convoluted. Hovering the mouse over the stacked icons unstacks them, and then as the mouse if held over the launcher the icons start scrolling up uncovering the now-flattened and covered icons. Remove the mouse from over the launcher and the icons re-stack.
Is this a better solution than just indicating, via shadows, that more icons exist down the launcher? I suppose it is, and I could see usability arguments being made so that the user can see all the icons, even if they're stacked and foreshortened. The problem is excessive launcher clutter. The more icons you add to the launcher the more the icons will stack. Too many stacked icons would look very messy and cluttered. And since the new behavior is to unstack and then slide the icons up to be clicked, I'm not so sure it buys you anything to stack them.