Actually, they aren't -- to their primary audience. That audience is not you. You have nothing to do with the message.
Graffiti are about the people who write them. It's a proclamation: I was here. You and I don't care that this particular young vandal was there. And Young Vandal doesn't care that we don't care. It's just for him, his buddies, and their rivals.
Sadly, a lot of fundraising is like that. It's all about the people who created it. It makes no attempt to connect with or communicate with others. It's a product of self-expression, not an attempt to connect.
It's the kind of fundraising that's chained to super-prescriptive brand guidelines that are focused on the greatness of the organization. Or that tries to "educate" donors into a proper understanding of the cause before they give. It's just an elaborate form of I am here.
Problem is, fundraising is supposed to motivate responses. When it's self-focused Graffiti Fundraising, it's just a waste of money. And time. And your donors' good will.
Don't do Graffiti Fundraising that merely proclaims your existence and awesomeness. Talk to your donors about their opportunity to change the world.