I always get a chuckle out of that ad you are referring to. There is no spamming here, no religious discussion, yet this religious ad shows up if you aren't using a AdBlock.(I don't know who in their right mind wouldn't use one, but.) I think the ads are there because sometimes allowing certain ads on your forum means you can use a specific service for free in exchange. I'm not sure.
I guess an example would be using a service that will provide you a logo in exchange for advertising their company. Again, I'm sure that we can all agree that a Bill Gates I am not. Just thought I'd comment anyway.