mommy - I don't think its unreasonable for you to not want to share your news until you are holding a baby in your arms. Announcing and then "taking it back" is the worst thing in the world. I don't blame you one bit. Those close to you will already know the baby is on the way; FB and other forums are mostly to keep in touch with distant friends/relatives that you don't talk to in real life, for the most part, imo.
Last year I put a baby announcement on my Christmas card and mailed it to 70 people, and gave it out at work to 25 coworkers. Then I found out 2 days before Christmas that I had lost the baby. It was gut-wrenching having to tell people that I had miscarried.
This year, even though I am 20 weeks and just ordered my cards, I did not mention baby on the cards at all. Last year is still too traumatic and I do not want a repeat of that. I have to believe that everything will end up OK with this baby, but I still cant put it on the cards...