I personally hate it passionately. All it takes is an idiot with a spray can to ruin a statue, monument, property or just space... it sickens me. And, while there are exceptions, most of the time the "artist" is just a pathetic teenager (or worse) who thinks he or she is a rebel because they can draw two lines of black paint on a wall or whatever.
But why do I hate it that much? Well...
There was a traveling art gallery coming to my neighborhood a few years back and, not two days after the fact, someone "tagged" all the frames with paint. Un-fucking-believable.
I also got to pay a visit to my beautiful hometown in 2009 and all I found was that EVERY landmark was completely ruined because of that.
And please don't even get me started on those who paint ponies on everything...