I did not write letters to my immediate family since I told them face to face, and then my parents informed my extended family, or at least my uncles and aunts.
However, I had the same consideration for my Facebook post when I announced my name change. I had decided to make the announcement, and then link to a new account which people could add, since "cleaning up" the original profile would be a a lot of work. Additionally, I felt like a fresh start, so switching profiles felt kind of symbolic. So unless someone decided to copy and paste the text elsewhere, it would only be up for around a week or so before I took the old profile down.
That said, posting a very personal, very detailed and "tough" (I've gone through a lot because I repressed my gender identity) text would still out me as having struggled intensely with self-injury, eating disorders, depression and so on. These things are sort of taboo for many people, and being open about them can be socially risky. At the same time, I figured it could prevent the "just a phase" nonsense some people might otherwise convince themselves of, and it would also make clear that this isn't something I do for fun or out of boredom, but a last, desperate attempt at making my life worth living.
The response was overwhelmingly positive; everything from cousins to priests to a former employer (whoops, didn't realize he was on my list) wrote highly supportive messages and thanked me for what I wrote. People who I haven't met in years or even more than a decade have contacted me and want to stay in touch again. I had one negative response, from a friend who has known about this for a year and been seemingly accepting but apparently didn't realize it was "real" until reading my text. He thinks it will be too difficult for him to get to know me as a woman, and never wants to meet me again, but still sees me as his friend. I call nonsense on the latter part, but if it helps him rationalize his choice... Lastly, of course many people did not say anything, some just added my new profile without commenting, some probably didn't see the announcement (though I repeated it thrice before deleting, since Facebook doesn't show everything to everyone), and some may have reacted negatively but had the decency to keep it to themselves.
To get to the point, many on my friends list are what you could call social conservatives. Many are deeply religious and have grown up with Puritanism, and their default mode would in many cases be to write me off in some way or another. However, I think the text I posted shocked them into a realization that this is a real phenomenon, which causes real suffering if not treated appropriately. And since they are, ultimately, good people, they prefer me choosing something foreign to them, over me being dead. However, if they did not know that death or a miserable life were the most probable alternatives, they might well have rejected me.
Now if all my friends were liberal, open-minded, knowledgeable people who needed no introduction to what being trans means, and perhaps already knew the suffering often connected to it, then a brief, matter-of-fact less personal note would suffice. I however needed to speak to people's hearts, to at least give them a chance to understand. I think this is what it boils down to; do you need to convince people, to change hearts, or will simple, neutral information suffice? With close family, I believe the former is often necessary, but there are probably exceptions. In the end, only you can know.
