When the trash can is empty, it looks nice and clean and sharp, the sort of trash can you'd carry about with you to impress people. When it is full, it looks dirty, and, when compared with the rest of the shiny icons on my dock, I feel a great need to empty it.
The thing that is broken about this interface element is that it looks full, even if there is only one teeny text file in the trash can. I don't need to know when there is at least one file in the trash can, I need to know when there are so many large files in the trash can that it needs to be emptied, so that I can download more anime. The trash can shouldn't ever be emptied, unless I need to free up some disk space -- emptying it at any other time is inefficient, and unnecessarily risks permanently deleting an important file.
So, there are really two problems here: the trash can tells me not when it's full, but when it has at least one file, which is useless information, and when it has at least one file in it, it tells me that I ought to empty it when I really shouldn't.
What I just did, to break the habit of compulsively emptying my trash can, was set it so that it always displays the empty trash can icon. If you're a Mac user, you can do this too, I found instructions at InterfaceLIFT. When you get to the part where it says "open .", instead, type "cp trashempty.png trashfull.png".
