According the website: "We at the Church of Google believe the search engine Google is the closest humankind has ever come to directly experiencing an actual God (as typically defined). We believe there is much more evidence in favor of Google's divinity than there is for the divinity of other more traditional gods."
They even provide a list of nine proofs to show the strength of their theory. They can be found here.
My favorite piece of hate mail?
"I'm sorry, but I must not only completely disagree with your little Googlism idea, but i must also call it insanely retarded."
Ah yes, this made my evening :-)