FYI, I am a lesbian.
Today is National Coming Out Day, which usually passes without much acknowledgement on my part. It's an opportunity for people to say "hey, I'm gay!" in a large group, which is theoretically a little bit easier than doing it alone. It also provides an example for people who might not be ready to come out or who might think they don't know any LGBT folks. If you want an example of why coming out is important on a personal level, read this post from Dear Sugar.
The first person I came out to was myself, and man was that a long and complicated process. Despite being raised in a liberal home, homosexuality was not really a topic of discussion during my formative years. Being by nature non-confrontational, even with my own feelings, I opted for asexuality as the safest course of action throughout high school and most of college. I read a lot of my mother's (straight) romance novels. I formed close attachments to other women, but did my best not to analyze that pattern of behavior. In retrospect, I suffered from internalized homophobia and was afraid I would lose friends and family members if I talked about my feelings.
I remember coming out to my parents when I was 21. While I was bracing myself for some sort of strong reaction, they responded in such a mild way that I realized that they'd probably known for years and had just been waiting for me to figure it out. I realize that most people likely don't have such an anticlimactic time coming out to their family, especially if they're living in Utah, but I was lucky. I consider myself lucky, because every time I've come out, the most I've gotten is a skeptical look. Aside from my grandmother, most of my family members took the information in stride.
You don't just come out once, and then you're done. It's a process that repeats over and over as you move to new places, start new jobs, and make new friends. It's the moment you talk to an administrative assistant and explain that you have a wife and you're legally married and you're going to be opting for the family insurance plan. It's the crossroads at which your new co-worker asks if your son looks more like you or your husband. You can choose to change the subject, or explain that the kid is lucky enough to have two moms. It's true that the world is changing, and coming out isn't as agonizing or dangerous (job or life-threatening) for someone like me, in my liberal corner of liberal Massachusetts, as it once would have been. However, there are still plenty of places where it's not easy, and the mere act of being gay is deeply frightening to other people. Everyone's circumstances are different, but coming out is one thing we can all share with each other. And that's why National Coming Out Day is still important.
ETA: I am, of course, coming out about different things all of the time, as I think everyone is. I'm a mom, I'm getting a divorce, I'm dating someone new . . . "coming out" is a way of saying "sharing something personal about yourself that you can't be sure how people are going to react to."