Clever Dock Improvement

Keith Lang has just posted a mockup of a clever improvement to Mac OS X's Dock:

'Stand Up' Mac Dock Mockup from Keith Lang on Vimeo.

His basic idea is that applications in the Dock would show some indication as to whether they are capable of opening the file the user is currently dragging. Even if you knew which application you wanted to drop a file on, Keith's system would help you find it more easily.

The workflow management software I work on uses a similar system to indicate possible drop targets in several of its editors; as soon as the user starts dragging an object, the editors indicate where it can be dropped. Similarly, I think Keith's idea could work outside of the Dock – in the Finder, for example – as well.

Update: Here's Keith's second iteration.