I like this a lot... I like the fact that people create gardens where one does not expect it.
Guerilla gardening is something that we will se more and more. People want more green in the cities
and unused space can be used to produce beauty and food. And to go through the normal route to get a permission etc is going to take too much time and most likely not lead to any garden. People take the spade in their own hans and just create a garden over night! What a wonderful surprise to wake and find a garden where before it was nothing.
Peter Richasen does this as a sort of street art and has become quite well known for it too. Check out his blog and maybe you get some ideas for how to beautify your own neighbourhood...