There is considerable discussion in the AA rooms about whether posting on Facebook breaks the anonymity agreements of AA. Anonymity is in place not just for your privacy and protection, but for protection of the group. The way this was explained to me is that if someone identifies publicly as an AA member, and then relapses, folks make associations with the efficacy of AA.
I am not a facebook person. It takes a lot of energy, energy which I would rather commit to a sober community like SR. I can be very open and full of enthusiasm here, and it helps others to stay sober and doesn't potentially damage me or anyone else.
My AA community is another place where I share my enthusiasm for sobriety. I have many AA friends who I spend time with outside meetings, and our shared sobriety is a theme in our friendship.
I am not in relationship right now, but would tell any prospective partner about my issues with alcohol and my commitment to recovery. I would not necessarily share that info on a first or second date, although I would be very open about not drinking/being abstinent.
I don't share my alcoholism info at work, because I feel it leads to preconceptions about my professional capacity. My secretary knows because, well, your secretary knows everything. I trust her and she often covers for me if I'm at an AA meeting.
I don't share much about it with my other friends and family, but they know that I'm actively in recovery. I've found that folks who drink socially (or family members with alcohol issues that they don't want to look at) don't understand the choice to be abstinent. The conversation never goes quite where I'd like it to (enthusiasm and support), but spirals into a place where I'm defending my choice to be abstinent or reducing the issue to details about my alcoholism which illustrate only a very limited aspect of my story.
I think the beauty of the recovery community is that it gives you a...recovery community - where you can openly share all your triumphs and struggles, your learnings and fears with people who relate and understand the scope of the journey.