One of my cousins just announced our other cousin's twins' birth on Facebook, complete with 'checking in' every family member on her friends list at the hospital, and posted the baby's names. Oh, and it was a public update - no privacy settings whatsoever. The cousin literally JUST had her c-section, so I know she didn't give the ok to announce.
The icing on the cake - my great aunt responded and said "Um, wow. What unusual names. Those will take some getting used to."
We will be sticking with the plan to not tell any of these people our baby has been born until after we get home. lol