I kind of agree and kind of don't! Personally yes it DOES annoy me when people go on and on and on about their pregnancy. But equally it is their page so if that's what they want to post about then that's totally up to them! I have a similar experience to Storked - losses and TTC issues so I also remember how hard it was to use FB for a long time, and I do worry about anyone who is going through the same thing.
It's nice to share exciting news and things but for me, I would never do that as a public status update - I know I can choose who sees my info, delete anyone I don't want to be friends with, but there are people on there who I want to be friends with yet at the same time don't think I really want them to know all the details of my pregnancy. I am just a bit private. I never announced my pregnancy on FB, I've never posted a scan photo, I've never put an update about symptoms, doc visits or whatever. The people who I want to know know, and we see each other often enough to catch up in person or private email so I have no need to put anything on FB.
I think that whilst it's probably a nice thing to do at the time, in 10 years time or whatever all those photos and memories are going to be buried under a decade's worth of useless info. In my mind it's much better to keep a journal, print out bump photos etc so you have something tangible you can look back on in the future, and share with your child if they want to look.