Cabel's got a great name for those odd gaps in buildings and street-furniture where people shove their garbage. He calls them "Litterplugs," and boy does he have a lot of great photos of them. We get a lot of these in London, thanks to the wide-scale removal of trash-cans.
I first noticed the “litterplugs” (if I may) phenomenon in Japan, ten years ago. This is the photo that started it all, a slightly bowing construction wall by Shinjuku station that immediately became a garbage can:
Since then, it was everywhere. Now, I can understand how generalized holes — containers, street light bases, flower pots — become makeshift trashcans. Even if they’re obviously in no way trashcans, and likely will never be emptied or cleaned by any human being on earth, and in most cases there’s a real trashcan mere feet away, they at least share a vague similarity to the raw concept of a trashcan.