I don't buy this thing about people just "sharing their happiness" on Facebook. Personally I think there is no need for it. Your true friends are people you would probably see in 'real life' anyway so they could share in your good news because they're in your life all the time. I do believe Facebook is mostly all about Top Trumps/Poker: "Oh I'll see your new house and I'll raise you a wedding...Well I'll see your luxury holiday and raise you a baby scan, read it and weep!" LOL! I deleted my account months ago, hooray!
It's a bit like way back when...before I got married, I was so sad that DH wasn't getting around to popping the question while I watched everyone around us get married. There was a girl on Facebook who updated her status about her wedding every day, to me it felt like a smack in the face and it really did seem like she was bragging about the fact she was getting married. It is possible to bridle all that "happiness" they have. I knew other girls like me who were dying to get married but it wasn't happening for them, so when I got engaged I vowed NEVER to brag on FB about wedding plans and things out of respect to those girls' feelings. I think even if it's not intended that way, it looks very "Oh look what I've got" and I find that kinda ostentatious and showy which isn't really something I can relate to. So in the same vein, I would never post scan pics/bump pics/baby tickers on Facebook out of respect for the feelings of other women who may be battling this horrible disease infertility. Instead, I will share my happiness in the real world with my friends and family, not to a bunch of acquaintances on Facebook. So I guess that is my "I promise when I get my BFP..."
Just my two cents