Nothing. You can fill out a form and be a minister in minutes. According to the website it's as legal as any other minister. you have to buy the credentials which is where they make the money. There is a short bio on what they believe which is basically "in science". So I would imagine church services would be more of a place where atheist can vent about dealing with religious infringements on their lives and organizing to keep it at bay in legislation.
That is whacked.
So they sit around at atheist church services and complain about something they don't believe in.
I looked at the site. This is laugh out loud funny.

FAQ
What do we believe?
The First Church of Atheism is formed around the belief that the mysteries of life can be explained through science and reason. We aim to provide a place for atheists to become ordained, for free, as well as a hub for atheists to find ministers to perform their ceremonies. This is our doctrine:
“Nothing exists besides natural phenomena. Thought is merely a function of those natural phenomena. Death is complete, and irreversible. We have faith solely in humankind, nature, and the facts of science.”
Is this really free?
Yes, becoming ordained with the First Church of Atheism is entirely free of charge.
Why is this free?
We believe that everyone should have the right to preach what they believe, to start a congregation, and to perform ceremonies. This is usually reserved for members of traditional religious sects. We have started a church of our own, based on our beliefs, and will provide our service of ordainment free to anyone who shares our beliefs.
Will I be a minister in the eyes of the law?
Yes, you will be a legally ordained minister. You will be able to perform every task that a clergy member can perform.
How do I prove I am an ordained minister?
Visit the store to purchase various items, such as an identification card, certificate, or letters for your local government office.
What type of services can I perform as a minister?
You will be able to perform the following services:
-Weddings
-Funerals
-Commitment ceremonies
-Many others
Are there any privileges of being a minister?
Ministers command a level of respect from the general public. Some parking lots have reserved parking for clergy. You will have clergy level access to prisons and hospitals.
How long does my ordainment last?
Your ordainment with the First Church of Atheism lasts for your lifetime. Once you are ordained, you never have to do anything again. You will be a minister for life.
Can I revoke my ordainment?
Yes, simply contact us and we will remove your ordainment, free of charge.
Can atheism really have a church?
A church is defined as an association of people who share a particular belief system. So yes, a church of atheism can really exist.
Where is the First Church of Atheism located?
The FCA is located in Langhorne, Pennsylvania.
Do you have a physical church that I can visit?
Not yet! To learn more about that, click here.
What do I have to do to start my own congregation?
Once you become an ordained minister, you can begin preaching to a congregation immediately.
Is Ordainment available worldwide?
Yes, Ordainment is available to people worldwide, though the legality discussed only pertains to American citizens. You will have to check your local laws, but most westernized countries have similar religious tolerance laws.
http://firstchurchofatheism.com/faq/