I'm open about my bipolar when it is relevant. Not just a need to know, but you know what I mean. You might know me for a year and not know or you might be in the checkout line with me and know.
I disclose at work to protect myself. I disclose to friends to help them grow in their perspective of mental illness. I disclose to further the intimacy of a relationship. I disclose if I see an opportunity to break the stigma. Or I disclose to a fellow bp to create a kinship.