Do you work with your screen laying flat, such that you're looking down on it?
I'm not being argumentative; there is a history of the "desktop" metaphor, where it did seem sort of like the user was looking down on it from above. That particular approach to the metaphor seems to have faded deep into history. Not saying it's wrong, just that we seem to have moved somewhere else with UI, and I feel like a corkboard with pieces of paper tacked to it is a more fitting analogy for the way many of our current desktops work. The way shadows are used in most current desktops match that metaphor more closely than objects on a horizontal "desk" surface. And, given that we never use screens sitting flat on a horizontal surface (even the Microsoft Surface evolved to go vertical). The ergonomics of staring straight down is pretty awful. Our heads get really heavy at that angle, causing back pain.
Edit: Some "desktop" metaphor UIs where a "top-down" light source might logically lead to OPs shadow design:
Even the modern take (Bumptop for Mac) seems needlessly cluttered and cumbersome to manage. Then again, I prefer tiled interfaces, so I lean toward the extreme on the other end of the spectrum.
I'm not being argumentative; there is a history of the "desktop" metaphor, where it did seem sort of like the user was looking down on it from above. That particular approach to the metaphor seems to have faded deep into history. Not saying it's wrong, just that we seem to have moved somewhere else with UI, and I feel like a corkboard with pieces of paper tacked to it is a more fitting analogy for the way many of our current desktops work. The way shadows are used in most current desktops match that metaphor more closely than objects on a horizontal "desk" surface. And, given that we never use screens sitting flat on a horizontal surface (even the Microsoft Surface evolved to go vertical). The ergonomics of staring straight down is pretty awful. Our heads get really heavy at that angle, causing back pain.
Edit: Some "desktop" metaphor UIs where a "top-down" light source might logically lead to OPs shadow design:
http://blog.codinghorror.com/content/images/uploads/2006/05/...
http://kruzeniski.com/wp-content/uploads/2011/04/how_print_i...
Even the modern take (Bumptop for Mac) seems needlessly cluttered and cumbersome to manage. Then again, I prefer tiled interfaces, so I lean toward the extreme on the other end of the spectrum.