It's not weird at all. I have never understood why other people feel it's necessary to post their lives online for everyone else to scrutinise.
It's a common thing, nowadays, to befriend a person you have met once at a social event and Facebook has purposefully made removing friends into a chore. When you do remove people, they suddenly bombard you with messages and make you feel like a bad guy. As a result of this, a lot of people end up with a friends list pumped full of random acquaintances.
Also, because of the terrible privacy controls on Facebook (and by the way, you can't even delete your account anymore, only deactivate it), you can never be too sure who is looking at your photographs, your basic information and where you reside. Even the random acquaintances of your closest friends and family could be viewing your information. Do you really know anything about these people? Are they safe? Do they deserve to stare at your baby photos? Or half-naked pictures of you exposing your bump? Do they really need to know when your baby is due? Or which hospital you are having your baby at?
Personally, the thought of some random staring at my pregnancy details/ pictures makes me feel very uncomfortable.
Also, don't forgot that, although it's your baby, the infant is in fact a mini human being. Do you really want them initiated onto a social network like Facebook from the early years of their life? It's like baptising a child and making them Christian when they don't have the ability to choose whether or not they even want to be a part of a religious community.