I don't hide my atheism but I don't really purposefully push it on facebook either. My religion on Facebook is listed as: None - Atheist. I post articles from time to time but typically they are science articles or political news. If anyone has posted a bible verse or said they will pray for me on my account I don't remember and I probably ignored it or deleted it. I don't feel like every post of a religious nature needs a response. I mostly use my facebook to keep in touch with people and I don't really want my page to turn into debate after debate. I enjoy debating but I also like to keep my debates in a setting where they don't easily get carried away. Facebook debates more often than not turn into flame wars and I'd rather interact and debate in a more mature way.
Exactly. The purpose of your Facebook page is to allow you to post things primarily about you, your life, hopes, dreams, beliefs and non-beliefs. Early on, I would go to theist friends on their pages and challenge their religious posts, but later I thought that in doing so, I was invading their "space" uninvited, so I limited my opinions (unless invited) to my own wall.
BTW: I actually get into more arguments with an agnostic buddy of mine who strongly disagrees with the statement that disbelief is the default position. In his way of thinking, the phrase "I don't know" doesn't imply disbelief. (but that's another topic).
I am not "open" or militant on fb in general, although in messages and chat, when the subject comes up on a one-on-one basis, I will tell the individual person with whom I am speaking that I am an atheist. I am always generous and easy in my admission, stating that I understand the other person is religious, but I am not, and that I hope this issue won't become a wedge in our friendship. I have found this approach works fairly well, and the individuals whom I have spoken with do seem to tone down their religious rantings a bit in general on fb, just knowing that some of their audience is not part of the choir. Making them deal with it on an individual basis with someone they genuinely like seems to make them just a little bit more aware of the diversity out there in facebook land.
Now, for the constant ranters sending up prayers for everything from sporting events to natural disasters, I know those people are unreasonable, and even though I might like them for some other reason and would like to keep them as friends, I don't want to listen to their crap, so I just take the easy route and whenever they post a Hail Mary, I hide the post so I don't have to look at it in my feed all day. It works really great! I also hide any political posts that annoy me, if I don't feel like counter-arguing, but neither do I feel like looking at the words all day in my feed. I find that if you leave these posts in your feed, they just eat at the edges of your mental health and annoy you all day. Make them disappear!
As for supporting the cause, I do as someone else mentioned -- I often post scientific links to try to continually help enlighten my fellow fb citizens.