Parents bragging endlessly about their kiddos can get kind of obnoxious to us non-breeders, but it's really more positive than negative the vast majority of the time- you're stuck with a crying poop machine that's totally dependent on you, so if you're happy about it and want to share the enthusiasm, at least that means you're probably in a good frame of mind to take care of your child.
That said, I've seen examples here and there of parents making ghastly choices (including, in some cases, the choice to be a parent in the first place when they absolutely should not have) and then looking to their friends and family for validation. It sickens me. I actively avoid being around those people because they make me so angry.
I have seen parents claim online they can't stand others bragging about their own kids. So they start saying things like "it's not a competition" "We're not in a competition" "Poor you."
I have learned that at Babycenter, saying good things about yourself or about your kids or what they have accomplished is "bragging." I never knew that was bragging so I have probably bragged about my own.
I have seen parents say they don't like seeing lot of photos of their friends babies on facebook or seeing what they post about them in their status such as about poop or pee, potty training, messy faces. Plus even the childfree have said the same.
Really, you can't win so I just do what I feel is right and not care what others think. I will post photos of my son on facebook, I will post some things about him on there too, I am guilt of posting his birthday photos and one of them was him with a messy face from his cake. I am guilty of having him in my FB profile picture and creating a whole page on him. I am guilty of using him as my avatar on WP and on Babycenter and having one of those tickers in my signature about him. There will always be someone out there who be critical about all this and act like it's all wrong and say what bad parents we are for it or attention whores.