I don't go out of my way to delete people I don't speak to, but I do lose friends over time, either people removing me, or people deleting facebook. The rate at which I lose friends is just slightly slower than the rate that I'm adding friends.
So it's not like the number is surrounded by an H1 tags.
And I don't tweet. I'm on Twitter, but I lurk. I think I have like 4 friends. But I follow about 25.
So where's the noise?
Edit: Ok I found the count. I didn't notice it at first. I have 537 friends on FB. So guess I'm an attention hound. :)
As for posting, neither me nor my friends use Facebook for chatting. It's photos and status updates about what we are doing or going to do. It's almost never questions, only statements. Then again, me and my friends are in our mid-thirties, none of us "grew up" with Facebook, none of us used it at university, and the common topics are work and kids and vacations.
I have a number of friends on Facebook that are younger around 20, extended family and the like, and they use it in a completely different way: They add more friends. They never remove friends. They have no critera for friends other than "doesn't dislike", it doesn't matter if they don't know the person well or not.
They also use it a lot more for public chatting. Someone posts a status update, and then two or three people have an unrelated conversation in the comments to that, because... it's an input field and it was there and they know the relevant friends will see it.
And that's just two different ways of using it, I'm sure there are a myriad more and I have absolutely no idea which way is the most common. But it's pretty clear from your post, and from the piece by Arrington that both of you bring your own biases into it. You both think that most other people have the same Facebook experience as you do.
So Arrington goes "Facebook sucks for me, therefore all of Facebook is broken!". You're much, much less egocentric, but still, I wouldn't make the bet that you did that the grandparent post's view was unique. :-)