According to what I've read, most graffiti is applied by juveniles, and they eventually grow out of it. When I was a kid, there were always other kids that wrote on the back of the seats when on the bus, or nicked milk money from doorsteps, or knocked over rubbish bins or smashed the heads off garden gnomes. They grew up and got over it, and they all came from good families and went to good schools. They simply ran wild when unsupervised, as they didn't have the self control to stop themselves from doing stupid things. As they got older, some graduated to getting drunk and smashing up a lot of cars.
Eventually, they worked out that actions had consequences, and that the consequences might not be pretty, and they calmed down and grew up. The wildness of youth was replaced by maturity, and they now have kids of their own that they are trying to raise to act in a civilised manner.
So do I have any answers?
No, not really. But I do think that a ban on spray cans is silly. I've used them myself, for touching up paint on cars and fixing up outdoor furniture and the like. I can see merit in slapping a tax on them in order to pay for cleaning up graffiti (let's say $3 a can - and don't ask me how much money that will raise - I am not the Treasury), but bans never work.
You can help to mitigate the ill-effects of graffiti and other malicious damage by cleaning it up as quickly as possible, and not dragging your feet like Telstra and RailCorp. By that, I mean removing it within 24 hours if you can. The deterrent effect of rapid removal is, if you ask me, much more powerful than a ban.
As I have mentioned before, only 119 people were charged in NSW with graffiti offences in 2006. That's less than one per Council area (there are 150 Councils in NSW). I'd prefer that the government tried to enforce the existing laws, rather than slapping new ones on us.