I'm also really afraid to tell people. Like, its hard for me to regard it as a "mental disorder" I much rather call it a "mood disorder" but its weird how labels can make all the difference. Saying "I'm mentally Ill" scares the heebee Jeebees out of me, and I'm MUCH more comfortable saying "I Have a mood disorder"
As for advice, I'd suggest only telling close friends and family. When you find yourself in a situation where you are trying to explain your behavior or feelings to someone, if you aren't that close to the person, you can say something like "well, there are reasons for the way I am, and no hard feelings, but I really don't want to discuss it right now" or if you do think you want to tell them, say "well, I can't really control it. I have this mood thing, like PMS on steroids, but I'm working on it" and if they ask for more info, you can specify bipolar, but the whole "PMS on steroids" thing should lighten the mood and make it a bit easier.

I'm guessing that the reason that there is tons of support for drug addiction verses mental illness is that people don't know as much about mental illness. They think of severe schitzophrenia, and are freaked out. They think voices, delusions, etc, and it scares them.

I hope this helps.