Drop only seems to work for a very short period after drag-entering

Steps to reproduce:
1. Navigate demobrowser to http://html5demos.com/drag
2. Drag one of the items over the dust bin and wait a little (a fraction of a second is enough)
Expected result: The dustbin should gulp up the item
Actual result: The item just appears in the list again.

When immediately releasing the mouse button after entering the image area with dust bin, the items get gulped up as expected.

It works in Chrome when holding the mouse button for a while.