I was pretty shocked when I was in Australia at how much graffiti there is about. There's lots in certain areas in England (usually around some train lines) but not so much where I live...in fact, it's so rare, it was a bit of a novelty to see it when I moved down South for 3 years.
I think that there's some talent with some people - but the lack of respect for the property of others winds me up. If you want to graffiti on your own house, go for it - but they should leave everyone else out of it.
And people who scrawl the same stupid tag over and over are somewhat missing the point, I feel.