Coming Out
I can count the number of people that I know personally who know that I am bi on one hand. These select few I have told because it came up, and because I knew they would understand. And they did.
Of course, that doesn't mean every one will be as tolerant and understanding. I believe that such a revelation would cause me no end to trouble at work, for example.
I've been told that it doesn't matter what other people think. For me, it's not a matter of what they think; I've not really concerned myself with that about any part of my life. It's more a comfort level, or a danger/no danger level. Sure it doesn't matter what they think, but I'd rather be safe than sorry.