A half-serious question. Why not take advantage of the tax shelter and collect some of that "faith-based" money? Perhaps it could be diverted to some better causes. I don't know all the details of this, but would there be an advantage over simply creating a non-profit charity group? Hostile religious types like to accuse atheism of being a religion itself all the time. (of course, the fact that they consider this an insult is obviously self-defeating)
I can see the dangers in it too, and how there may be no desire to be considered a "religion" in any way. I can also envision Creationists using this as ammunition to argue that teaching evolution in schools is advancing a religious agenda. (just the kind of irony they love! see above...)
In fact, I looked up "religion" in the Merriam-Webster dictionary, but all the definitions included either "faith" or a belief in the "supernatural." It is BY DEFINITION irrational! However a "church" could be a "place of public worship" and "worship" can be "to regard with great or extravagant respect, honor, or devotion." A Church of Atheism could be a place to worship rational thought, or the human spirit, etc.
Anyone know how a religion is defined by the law? (I'm thinking of the U.S. simply because I live here)