It's usually really ugly and poorly executed, so I generally hate it. Once in a great while I will see something that is clever or well-done by someone talented, and I can admire the creativity, but it still is vandalizing someone's property and that just isn't right. If you pay a mortgage on a building, you don't want some idiot coming along and wrecking it with paint. If a landlord commissions it, that's fine, but it is still usually pretty ugly even then.
The world opens up... when you do.
Oh, oh, can't you see? Love is the drug for me. ~Bryan Ferry
"Love is that condition in which another person's happiness is essential to your own." ~Robert Heinlein