Actually, the theory I've heard that makes the most sence is they are paying for it and some (obviously lame) computer program picked our site due to our frequent use of words like "god". A slightly less lame program would notice that invariably it is in sentences such as "Believers in god sure are stupid."
No Christian banner, but on the main site there is a Muslima matrimonial banner on top, seems there are a lot of Muslim girls looking for western husbands.
But then again, that's the way internet works, they use keywords. For the fun of it, just view the 'ads by Google' on newspaper websites, especially those with reports about birth defects, or murders etc. They sometimes are nothing but hilarious!