I decided to come out to those close to me, basically because that I realized I was never going to be happy any other way, I had tried so long to attempt to "beat" my feelings, but at the end of that long war against myself I realized that you can't win a war against who you are.
I came out to the people close to me, because it otherwise I wouldn't be able to take the steps I need to transition, at least not without a great deal of difficultly. For example, I have quite a few clothes, I am not sure where I would put them if weren't out.
Most people not close to me, don't know yet, the reasons are basically that it is none of their business and I don't have to yet, everyone is pretty content with me having long hair, wearing makeup, etc so I can go reasonably far with things before it starts to become really obvious that something larger is going on.
I intend to basically keep things like this after transition too, i will never be able to be "stealth" to the people close to me, when you tell them you are trans, you can't untell them, but for people not close to me, I don't think it is really any of their business unless they are in some way affected by it.