The writing on the wall...
The term is from the ancient Greek, referring to the cleaning and re-use of a parchment for new writing. It's a good description of what goes on with aerosol art, too. The writers create art on a clean wall, the authorities overpaint it, the writers create new art on top of the old: a palimpsest in the full meaning of the word.
There are two players in the game: the writers and the authorities.
The role of the authorities
When I started recording aerosol art sites, it seemed to me that the biggest risk to these works was from the authorities painting them over. There are many sites around the town where this has happened. But now I think there may be bigger threats: damage from the weather and sunlight, damage from toying, and the of lack of good sites to write.
In recent weeks I've visited various sites where there are old works. The colours are fading, they've been toyed (scribbled on by others with lesser talent ), and there's not much space left to create new works. On these sites, it would be a blessing to have the authorities paint over the existing works and thereby provide new work areas.
The contest between writers and authorities is a dynamic one: to create artworks on the one hand and to create clean wall space on the other. There's a strange symbiosis: without one, there's no opportunity for the other.
So I think what's needed is a tacit recognition by the authorities of the right of the writers to create their works, and the recognition by the writers of the value of the authorities cleaning things up every so often. The important thing is to strike a balance: to leave the artworks in place long enough for them to create a lively art forum, but not so long that they are all toyed, faded and the space all used up.